
Class ^^iJ^ 



CopigtoK?„. 



'<?' 



i1 



COPYRIGHT' DEPOSm 



^ 






ELEMENTS 



MODERN CHEMISTRY. 



By ADOLPHE WURTZ, 

MEMBER OF THE INSTITUTE, HONOUARY DEAN AND PROFESSOR OP 

CHEMISTRY OF THE FACULTY OF MEDICINE OF PARIS, MEMBER 

OP THE ACADEMY OP MEDICINE, ETC. 



TRANSLATED AND EDITED, WITH THE APPROBATION OF THE AUTHOR, 
FROM THE FOURTH FRENCH EDITION, 



By WM. H. GREENE, M.D., 
*■ 

FORMERLY DEMONSTRATOR OF CHEMISTRY IN JEFFERSON MEDICAL 

COLLEGE, PHILADELPHIA, MEMBER OF THE AMERICAN 

PHILOSOPHICAL SOCIETY, OF THE CHEMICAL 

SOCIETIES OF PARIS AND BERLIN, ETC. 



WITH ONE HUNDRED AND THIRTY-TWO ILLUSTRATIONS. 



( 



>. 1879 

P III L A D E l1? H I A : N> . 0^ WA 

J. B. LIPPI^COTT & CO!'""" 

LONDON: IG SOUTHAMPTON ST., COVENT GARDEN. 
1879. 




^' 



\ 



-^ .<^ 






'h 



Copyright, 1879, by J. B. Lippincott & Co. 



r 



PREFACE TO THE AMERICAN EDITION. 



This book is translated from the fourth French edition by 
my pupil and friend, M. Grreene, whose perfect familiarity with 
the French language and thorough competence, at the same 
time, in chemistry I have had occasion to appreciate. The 
translation is, then, a faithful, or even improved, representation 
of the original work, in which he will certainly have detected 
and corrected some faults. 

The French editions succeed each other rapidly, showing 
that this little book responds to an educational need. 

It has been the endeavor to keep it up with the current of 
the latest discoveries, and in it to condense a considerable 
number of exact and well-selected facts, without banishing the 
theory which binds them together. Thus, the origin and foun- 
dation of the atomic theory have been given, as far as possible, 
in historical order. The notions concerning atomicity, so im- 
portant for the appreciation of the structure of combinations 
and for the interpretation of chemical reactions, are presented 
in an elementary form. 

The reader will remark that the history of the metalloids 
is relatively more developed than the remainder of the book. 
Indeed, this is the fundamental part of chemistry, and a fa- 
miliar knowledge of it is indispensable to the fruitful study of 
the metals and of organic chemistry. It is also the most at- 
tractive portion for beginners, for it is the most easily under- 
stood. 

Immediately on entering the immense domain of organic 

3 



4 PREFACE TO THE AMERICAN EDITION. 

chemistry, we find the facts overwhelmingly numerous and 
complicated. Among all these fiicts a severe and careful 
choice has been made, the historical importance and the theo- 
retical and practical interest of the compounds described being 
borne in mind. In this respect many additions have been 
made to the third French edition. Thus, the question of 
isomerism, upon which the theory of atomicity has thrown so 
much light, has been treated in a more thorough manner. 
The chapter on the aromatic compounds has been considerably 
augmented. 

The author hopes that these " Elementary Lessons" will be 
well received by the new public to whom they are presented, 
and that they will contribute to render attractive and diffuse 
the knowledge of the science to which he has devoted his life. 

ADOLPHE WURTZ. 

Paris, November 20, 1878. 



TRANSLATOR'S PREFACE. 



It is a privilege to be able to bring before the English-read- 
ing public a work by one who has justly won the reputation of 
being the most able thinker and perspicuous teacher of France. 
M. Wurtz is the acknowledged leader of modern chemical 
philosophy, and his labors have firmly established many of 
the views which long remained unaccepted by the majority 
of chemists, but which are now regarded as essential to the 
science. 

This book is therefore a brief but accurate embodiment of 
modern chemical ideas, arranged in such a form that the most 
difficult principles are acquired gradually in the course of the 
descriptions. 

Only such changes and additions have been made as would 
necessarily accompany the change of scene in which the book 
appears ; among these are the few American mineral waters 
mentioned, and other mineral resources of the United States, 
naturally interesting and important to the American public. 

WM. H. GREENE. 



1* 



ELEMENTS OF MODERN CHEMISTRY. 



INTRODUCTrON. 

The material objects surrounding us present striking and 
infinite differences. Sulphur is readily distinguished from 
charcoal, rock-crystal from flint, iron from copper, water from 
spirit of wine, and wood from ivory. It is known to all that 
these bodies differ not only in form, density, and structure, but 
also in their proper substance. They differ, too, in the changes 
through which they pass under the same conditions. When 
subjected to the action of heat they receive very differently the 
impression of that force. They become heated more or less 
quickly, and transmit the heat with greater or less rapidity 
throughout their own substance. A short bar of iron cannot 
be grasped iti the hand by one extremity if the other be heated 
to redness ; under the same conditions a cylinder of charcoal 
may be handled with impunity. Communicate sufficient heat to 
water and it is converted into steam ; remove heat from it, and 
if the cooling be sufficient, it is frozen into ice. Spirit of wine 
cannot be congealed by the most intense cold known. If a 
magnet be placed among iron filings they attach themselves in 
tufts around the two poles ; on the contrary, copper filings are 
indifferent to the magnetic attraction. 

Rock-crystal is transparent to light ; flint is opaque. These 
two bodies are unalterable by fire. They may be heated to red- 
ness in a furnace, but after the temperature has abated they 
will be found with their original characters unchanged. It is 
very different with the coal which we burn in our grates. This 
body disappears during the combustion, and leaves only a quan- 
tity of ashes. But it has not been destroyed, and its substance 
is found in entirety in a certain gas produced by the combus- 
tion. Like charcoal, sulphur is combustible, and is converted 
by burning into a gas, the suffocating odor of which is well 
known. 

Neither sulphur nor charcoal undergo any alteration when 

7 



8 ELEMENTS OF MODERN CHEMISTRY, 

exposed to damp air ; it is not tlie same with iron. In a moist 
atmosphere this metal experiences a striking and Listing change. 
Its surface becomes covered with rust and is no longer iron. 

In the forests, the leaves which fall and remain upon the 
moist soil are slowly consumed and disappear in the course of 
seasons. 

All of these changes, these phenomena, take place daily be- 
fore our eyes, and are familiar to all of us. On comparison, 
striking differences are discovered between them : some are but 
passing, and do not affect the proper nature of the body. They 
are the results of forces which act at. sensible distances, and 
which leave the body in its primitive state as soon as their 
action has ceased. A piece of soft iron is attracted by the 
magnet before contact is established, and when under the mag- 
netic influence, is capable of attracting other soft iron in its 
turn : the action of the magnet has made the iron itself mag- 
netic, but it immediately loses this property when the magnet 
is withdrawn ; and further, this momentary change in property 
has brought about no alteration in the intimate nature of the 
iron. It is found after the experiment in precisely the same 
condition as before. 

In the same .manner, rock-crystal undergoes no change in its 
specific identity by the passage of a ray of light. Withdraw 
from the vapor of water the heat which has been communi- 
cated to it, and the liquid water is recovered with all its prop- 
erties. Restore to the ice the heat which was abstracted in its 
formation, and water is regenerated as before. This is charac- 
teristic of the changes produced by pliysical forces. Under 
the influence of such forces, bodies experience modifications 
more or less profound, more or less lasting, but which never 
affect their specific nature. 

But the iron which rusts undergoes a complete and lasting 
change in its properties and in its substance. The rust is no 
longer iron, and vainly would it be sought to isolate the metal 
by mechanical means, or to discover its presence by the aid of 
the most powerful microscopes. The metal has disappeared as 
such ; it has undergone a complete transformation ; it has be- 
come another body. It has attracted one of the elements of 
the air, oxygen, and has, moreover, fixed to itself the moisture 
of the atmosphere. These latter bodies, which differ from iron 
in substance, have intimately united with the metal itself, and 
the result of this union, of this comh'uiation as it is called, is 



INTRODUCTION. 



9 



a new body, rust or hydrated oxide of iron. In this case the 
aheration is profound, the change is lasting ; the specific nature 
of the body is affected. This is characteristic of chemical 
action. 

In the same manner, when the charcoal and the sulphur are 
burned in the air, they attract oxygen and combine with it, 
forming two new; bodies that are called carbonic and sul- 
phurous acids. 

These phenomena may be rendered more clear by simple and 
well-known experiments. 

Experiment 1. — A globe (Fig. 1) is filled with oxygen, a 
gas which constitutes one of the elements of the atmosphere, 
and which is eminently fitted to support combustion ; into it is 
plunged a morsel of charcoal lighted at one end ; immediately 
the coal glows with a brilliant light, the combination takes place 
actively, and the charcoal is rapidly consumed. But presently 
the light becomes paler, the combustion ceases, and the char- 
coal is extinguished. The oxygen is now nearly or quite con- 





FlG. 1. 



Fig. 2. 



sumed, and the globe is filled with another gas which is no 
longer oxygen, although it contains that oxygen. It contains 
also the matter of the charcoal which has disappeared, and 
these two bodies have combined to form a new body, which is 
carbonic acid. This latter will not support combustion, and 
further, it extinguishes burning bodies. It is then a body 
having entirely new properties, and is formed by a chemical 
action. 

JExj)eriment 2. — Into another jar filled with oxygen (Fig. 2) 
is plunged a spoon containing ignited sulphur. The combus- 



10 ELEMENTS OF MODERN CHEMISTRY. 

tion takes place witli a beautiful blue flame, and in burning in 
the oxygen with so much energy, the sulphur unites with the 
gas and forms with it a new body, which is called anhydrous 
sulphurous acid. It is a suffocating gas, which extinguishes 
flame. It reddens, and afterwards bleaches, a solution of blue 
litmus poured into the jar. These are special properties which 
do not belong to the oxygen at first contained in the jar. They 
characterize a new body, the result of the combination of the 
sulphur with the oxygen, and formed by chemical action. 

Carbon, sulphur, and oxygen are simple bodies or elements. 
They are so called because from neither of them can more than 
one kind of matter be obtained. But when the charcoal in 
burning unites with the oxygen, the carbonic acid which re- 
sults from the union contains two kinds of matter, — carbon and 
oxygen ; and these two elements are united in such an intimate 
manner that the body which contains both does not resemble 
either carbon or oxygen : it is endowed with new properties 
which do not in any manner recall those of the elements which 
constitute it. In fact, it is a new substance, a compound hody 
formed by the combination of the matter of the charcoal with 
the matter of the oxygen. 

Considering the preceding facts, we may give to chemistry 
the following definition : chemistry studies those intimate ac- 
tions of bodies upon each other which modify their natures 
and cause a complete and lasting change in their properties. 

Iron may be reduced to a fine powder. This may be mixed 
with sulphur itself reduced to powder, and if the mixture be 
sufficiently intimate, it will present neither the lemon-yellow 
color of sulphur nor the gray-black of finely-divided iron. 
Nevertheless, a homogeneous substance cannot be formed in 
this manner. If the powder be examined under the micro- 
scope, the particles of iron may be recognized disseminated 
among those of the sulphur, but not confounded with them. 
By the aid of a magnet the iron may be separated. On the 
otlier hand, if the mass be thrown into water, the particles of 
iron will sink first to the bottom, while the lighter particles of 
sulphur remain in suspension. Thus, after having triturated 
the sulphur and iron together, not only can each substance be 
recognized in the mass, but they can be again separated by 
mechanical means. Here there has been no chemical action, 
but simply a imxttire. If, however, this mixture be heated, 
the sulphur will first be seen to melt, and afterwards the 



INTRODUCTION. 11 

whole mass will blacken and enter into fusion if the tempera- 
ture be sufficiently elevated. After cooling, it is perfectly lio- 
mogeneous, and neither iron nor sulphur can be recognized. 
Both have disappeared as such, and in their place is found a 
substance having new properties ; it is the sulphide of iron. 

They have disappeared, but their substance is not lost ; and 
it may be proved by experiment that the weight of the sul- 
phide of iron produced is exactly equal to the sum of the 
weights of the iron and the sulphur. The ponderable matter 
of the iron is then added to the ponderable matter of the sul- 
phur, and has formed with it a union so intimate that there 
results a new body, the smallest particles of which are per- 
fectly similar to each other and to the entire mass. This ex- 
ample and a thousand others that might be given prove that 
when bodies combine there is neither loss nor creation of mat- 
ter. The result of the combination, that is, the compound 
body, contains the whole of the substance and nothing more 
than the substance of the combining bodies. This is an essen- 
tial characteristic of chemical combination. 

The force which presides over chemical combination is called 
affinity. It is important that this force be distinguished from 
another which is often opposed to it, and which is cohesion. 

In order to reduce to powder a solid substance, such as 
pyrites or sulphide of iron, it is necessary to overcome the 
resistance opposed by the particles of the mass to their separa- 
tion. This resistance is due to a special force, which brings 
and maintains in relation to each other the homogeneous par- 
ticles of the sulphide of iron, as indeed of all solid bodies. 
This is cohesion. The particles which are bound together by 
this force are not only those minute particles which are visible 
to the naked eye or under the microscope, and of which the 
most impalpable powder of a solid body is composed. Such 
particles still present a magnitude that can be measured ; they 
must be considered as little masses, so to speak, indivisible by 
the mechanical means at our command, but formed in reality 
of particles still smaller. These smallest particles of a solid 
body which are bound by cohesion are called molecules. They 
are not in immediate contact with each other. In a perfectly 
compact and homogeneous mass, such as sulphide of iron, the 
molecules do not touch each other. Between them exist 
spaces of considerable magnitude, compared to the real volume 
of the molecule. This idea must not be confounded with po- 



12 ELEMENTS OF MODERN CHEMISTRY. 

rosity, which is caused by those accidental spaces which form 
visible pores in solid bodies. These intermoleciilar spaces are 
those which separate the molecules of a homogeneous and com- 
pact solid body, and physicists have further been led to believe 
that even in sohd bodies the molecules are not perfectly immo- 
bile, but that they execute vibratory movements in the spaces 
which separate them, at the same time maintaining their own 
relative positions. 

If a solid body be heated, a part of the heat is employed in 
raising the temperature, another part serves to increase the 
distances which separate the molecules : the body expands in 
becoming heated. But, as the distances between the molecules 
increase by the action of the heat and the effect of the expan- 
sion, the molecular attraction necessarily becomes more feeble. 
Cohesion is thus somewhat diminished, and if the heat be 
further increased, it may be so much diminished that the mole- 
cules, which have thus far been maintained in definite rela- 
tions, can move and glide freely over each other ; the solid 
body then enters into fusion : it becomes a liquid. The liquid 
state is produced by a diminution of cohesion, and is charac- 
terized by a greater mobility of the molecules. 

But if the liquid body be still further heated, at a certain 
point the additional heat may produce such a separation of the 
molecules that, already freed from all mutual attraction, they 
become completely independent of each other. This is char- 
acteristic of the gaseous state. 

It may be stated, then, that cohesion is considerable in solid 
bodies, but slightly energetic in liquids, and null in gases, and 
we have just seen that heat, by causing the changes of state of 
a body, can overcome and even practically abolish this physical 
force. 

Chemical force or affinity is at the same time more intimate 
and more powerful. It modifies the molecules themselves. It 
brings heterogeneous substances into intimate relations, and 
thus produces new molecules. A consideration of the examples 
already cited may indicate more clearly the meaning of this 
important proposition. 

We have brought together sulphur and iron, and by their 
reciprocal action and the aid of heat there has been formed a 
new body, — sulphide of iron. We know that the smallest mass 
of sulphur we can obtain is composed of a collection of per- 
fectly homogeneous molecules, aggregated by cohesion. In each 



INTRODUCTION. 13 

of them but one kind of matter can be found. It is the same 
with iron : the particles of this metal are perfectly homoge- 
neous. Sulphur and iron are simple bodies or elements. 

Let us now consider the sulphide of iron which results from 
their combination. This body also is formed of a collection of 
molecules, bound together by cohesion and perfecth^ similar to 
each other, but not homogeneous, for in each molecule we dis- 
tinguish two kinds of matter, — sulphur and iron. 

It cannot be admitted that these two substances are con- 
founded in the molecule, or that the effect of the combination 
of sulphur with iron is an interpenetration of the two bodies 
so intimate that they both disappear in what might be called a 
homogeneous mixture. On the contrary, it is supposed that 
the combination results from the juxtaposition of two infinitely 
small masses, each of which possesses a real magnitude and a 
constant weight. 

These little masses that no force, chemical or phj^sical, can 
divide further, constitute the atoms. In each molecule of sul- 
phide of iron there exist two of these masses, — one of sulphur 
and one of iron ; and the atom of sulphur and the atom of 
iron are bound together, but not confounded, by chemical force. 
And when sulphur combines with iron it is because the atoms 
of the sulphur arrange themselves in juxtaposition with those 
of the iron, and it is affinity which brings about the action. 

When these atoms again separate, the sulphide of iron is said 
to decompose. When it attracts the atoms of another body, it 
is said to combine with that body. 

If sulphide of iron remain for some time exposed to moist 
air, its surflice becomes covered with an efflorescence formed of 
a saline matter. In this case it has attracted one of the ele- 
ments of the air, oxygen, with which it has combined to form 
green vitriol or sulphate of iron. 

The molecules of oxygen, upon which cohesion has no hold, 
the body being gaseous, are each formed of two atoms, but 
these atoms are of the same kind ; the molecules of sulphide 
of iron, on the contrary, are each formed of two unlike atoms, — 
one of sulphur and one of iron. These latter attract four atoms 
of oxygen, which constitute two molecules of that gas, and 
these group themselves around the atom of sulphur and the 
atom of iron, forming with them one single molecule, more 
complex than the primitive molecule of sulphide of iron, for 
it contains in addition four atoms of oxygen. 

2 



14 ELEMENTS OF MODERN CHEMISTRY. 



1 molecule 1 molecule 
sulphide of iron. oxygen. 


1 molecule 
oxygen. 


© © 


00 


' fixes i^^^ 


and there results 

1 molecule 
sulphate of iron. 





0-0-0 




It is seen from what precedes that the words molecule and 
atom are far from being synonyms. The chemical molecule 
constitutes a whole of which the atoms form the parts, and 
these atoms are held together by affinity. In the preceding 
figure, this exchange of affinities between the atoms is indi- 
cated by lines of union. 

Chemical molecules have been well compared to edifices : 
the atoms constitute the materials, and it is readily conceived 
that such molecular edifices differ from each other accordins; 
to the nature, number, and arrangement of the atoms, that is, 
the materials composing them. 

An edifice may be enlarged by the addition of new parts : it 
may be reduced in size or it may be entirely demolished. In 
the same manner a chemical molecule may be increased by the 
annexation of new atoms, or diminished by the separation of 
some of those which it already contains. In the first case 
there is combination, in the second, decomposition. 

We may still further consider these phenomena of combina- 
tion and decomposition. 

Since the combination of two bodies results from the recip- 
rocal action of their atoms, and has for eff'ect a chang-e in the 
nature of the molecules, it is evident that it can only take 
place when these atoms, and consequently the molecules, are 
brought into intimate relations ; or more precisely, when the 
molecules of one of the bodies enter within the sphere of 
action of the molecules of the other body. And this sphere 
of action is very limited, for the affinity or elective attraction 
of the atoms is only exercised at infinitely small distances. 



INTRODUCTION. 15 

It results that affinity is often retarded by cohesion, wliicli 
maintains the relations between the molecules of a solid body. 
These two forces are frequently in opposition, and that the 
first may attain the supremacy it is necessary that the other 
shall yield. To make manifest or to increase the affinity be- 
tween two bodies, it is then necessary to diminish their cohe- 
sion. On this condition the molecules can enter within the 
spheres of their reciprocal attraction, and the atoms of one 
body can attract those of the other. 

It has been seen from one of the experiments already cited 
that in order to combine iron with sulphur it is necessary to 
elevate the temperature. Now, the heat, by fusing the sul- 
phur, diminishes its cohesion, and, giving its molecules freedom 
of motion, puts them into more intimate contact with those of 
the iron. Chemical action then commences. 

Instead of heating the sulphur and iron to bring about 
chemical action, it would be sufficient to moisten the mixture 
with water. By the intervention of this liquid the particles 
of sulphur and of iron are, as it were, cemented together and 
thus brought into more intimate relations. For a stronger 
reason can chemical action between two solids be facilitated by 
dissolving them both in water and mixing the solutions. Dis- 
solved, they themselves assume the liquid state and lose, in 
great part, their cohesion. The ancients understood the in- 
fluence of the liquid state upon reactions, and stated it with 
exaggeration : Corpora non agunt nisi solata. 

Although the liquid state facilitates chemical reactions, it 
does not follow that it always determines them. Frequently 
liquids and even gases, after being mixed, must be heated 
before they will react upon each other. 

Ea-perwient. — In a glass tube (Fig. 3) two gases, oxygen 
and hydrogen, are mixed in the proportion of one volume of 
the first to two of the second. Although the mixture is per- 
fectly homogeneous and very intimate, and although the cohe- 
sion of the gaseous molecules is null, no action takes place. 
But as soon as the mixture is heated by approaching a lighted 
taper to the mouth of the tube, combination takes place ener- 
getically. An explosion occurs and the two gases unite, form- 
ing water. In this case the heat has determined combination 
by increasing the intensity of the movements which animate 
the molecules of each gas, and so bringing the molecules of the 
one within the sphere of attraction of those of the other. 



16 



ELEMENTS OF MODERN CHEMISTRY. 



The electric spark produces the same eifect, and it probably 
acts by the heat which it communicates to the mixture. 




Fig. 3. 



More rarely combination is brought about by the influence 
of light. 

If a small bottle be filled with a mixture of equal volumes 
of hydrogen and chlorine gases, and then thrown into the air 
so that it may be struck by the direct rays of the sun, the 
combination of the two gases takes place instantly and with 
explosion. 

Such are some of the conditions which favor or determine 
chemical combination. Let us now study the circumstances 
which accompany these phenomena. 

Experiment. — If sulphur be strongly heated in a small glass 
flask until it begins to boil, and some copper turnings be then 
thrown into the flask, a brilliant incandescence takes place im- 
mediately. It is produced by the combination of the two 
bodies. Charcoal, sulphur, and phosphorus produce a brilliant 
light when they are burned in oxygen. Their combination 
with the gas takes place with evolution of luminous heat. 

Whenever a combustible body of whatever nature burns in 
the air, the heat and light are developed by the combination 
of the body with oxygen, one of the elements of the air. In 
general, all chemical combinations give rise to the production of 
heat, more or less intense ; in certain cases it is luminous, but 
more often it is obscure ; sometimes it is scarcely perceptible 

While heat acts as the determinin 



cause of a great number 



INTRODUCTION. 17 

of combinations, and while it is the result of such combination, 
it may play still another role in chemical reactions. In place 
of favoring combination, it may act in the opposite manner, 
separating atoms which are united by chemical attraction. 

Mercury retains indefinitely its brilliant surface when ex- 
posed to the air at ordinary temperatures, but at a temperature 
near its boiling-point it slowly attracts the oxygen of the air, 
and becomes covered with an orange-red powder, which is oxide 
of mercury. In this case heat has assisted the formation of a 
compound. 

If, however, this red powder be heated in a small retort to a 
temperature near redness, it is again resolved into mercury, 
which appears in drops in the neck of the retort, and into 
oxygen which may be collected. 

In this case an intense heat breaks up the compound which 
is formed at a temperature less elevated ; it occasions a decom- 
jposition. 

Heat acts thus in a great number of cases. A body is said 
to decompose when the elements composing it are separated 
from each other. 

The electric spark may occasion such separation when it is 
passed through compound gases. If a series of electric dis- 
charges be passed through ammonia gas, the latter is decom- 
posed^ that is, resolved into its two elements, — nitrogen and 
hydrogen. 

In like manner, the current of the voltaic pile decomposes 
a great number of chemical compounds, the elements of which 
separate and appear, each at its appropriate pole of the bat- 
tery. The decomposing action exerted by the galvanic current 
upon chemical compounds was discovered about the commence- 
ment of the present century by Nicholson and Carlisle. These 
physicists were the first to decompose water by the voltaic 
current. 

Lastly, light may decompose certain bodies, among which 
are a great number of the compounds of silver. The art of 
photography is founded upon the decomposing action of light 
upon certain of these combinations. 

There is a certain class of decompositions which it is impor- 
tant to consider with attention. They are occasioned by the 
intervention of more powerful affinities than those which main- 
tain united the elements of a compound body. 

If copper be heated in the air, it attracts oxygen and is con- 

2- 



18 



ELEMENTS OF MODERN CHEMISTRY. 



verted into a black powder, a compound of oxygen and copper, 
which is called oxide of copper. The affinity which unites the 
two bodies is considerable ; it cannot be overcome hj the ac- 
tion of heat alone ; at any ordinary temperature to which the 
oxide so formed may be exposed, the atoms of copper still re- 
main intimately associated with those of the oxygen. But if 
this oxide be mixed with powdered charcoal and then heated, 
a moment arrives when the affinity of the charcoal for the oxy- 
gen is superior to that of the copper. The atoms of oxygen 
then abandon the copper and combine with the cliarcoal, thus 
forming a new compound, carbonic acid, which is disengaged 
in the form of gas. Here there is at the same time decompo- 
sition and combination. The molecules of oxide of copper are 
decomposed ; those of carbonic acid are formed. 

Nothing is created in combinations ; nothing is lost in de- 
compositions. In the preceding experiment only copper re- 
mains )' the charcoal and oxygen have disappeared, but their 
substance is not lost. All of the matter of the charcoal is 




Fig. 4. 

found combined with all of the matter of the oxygen in the 
product of their combination, the carbonic acid, in such a 
manner that the weight of the latter added to the weight of 
the copper remaining, exactly represents the weight of the 
oxide of copper and charcoal. 



INTRODUCTION. 19 

Experiment. — Some oxide of mercury, of which we have 
seen the decomposition by heat, may be placed in a tube 
through which is passed a current of hydrochloric acid gas, a 
gas composed of chlorine and hydrogen (Fig. 4). An ener- 
getic reaction takes place. The orange-red powder is converted 
into a white crystalline substance, and much heat is produced. 
At the same time a small quantity of liquid condenses in the 
bulb. This is water, and the white powder formed is mercuric 
chloride, or corrosive sublimate, a compound of mercury and 
chlorine. The hydrochloric acid has converted the mercuric 
oxide into mercuric chloride. The mercury, at first combined 
with oxygen, is now combined with chlorine. But what has 
become of the oxygen ? It has combined with the hydrogen 
of the hydrochloric acid, forming water. We have brought 
into presence of each other two compound bodies : 

Mercuric oxide, 
Hydrochloric acid, 

and from their reciprocal action two new compounds result : 

Mercuric chloride, 

Water or oxide of hydrogen. 

This reaction has then occasioned an interchange of elements. 
The mercury of the mercuric oxide has combined with the 
chlorine of the hydrochloric acid, and the oxygen has left the 
mercury and combined with the hydrogen, which was aban- 
doned by the chlorine. The reaction has been as easy as 
energetic, thanks to the intervention of two affinities, for the 
affinity of chlorine for mercury has been aided by that of hy- 
drogen for oxygen. Two molecules are decomposed, and two 
new molecules are formed by an exchange which may be rep- 
resented in the followino- manner : 

o 
BEFORE THE REACTION. 

Mercury + Oxygen r= Mercuric oxide. 
Hydrogen + Chlorine == Hydrochloric acid. 

DURING THE REACTION. 



Mercury Oxygen 




AFTER THE REACTION. 

Mercury + Chlorine = Mercuric chloride. 
Hydrogen + Oxygen = Water. 



20 ELEMENTS OF MODERN CHEMISTRY. 

Such reactions, characterized by an interchange of elements, 
are called double decompositions. They are the more usual 
reactions in chemistry. 

The examples cited have been demonstrated by experiments 
easy to comprehend and to repeat, and are sufficient to give an 
idea of chemical phenomena. We have seen how, on the con- 
tact of two heterogeneous bodies, this elective attraction, which 
is called affinity and which sets in motion the smallest particles 
of bodies, comes into play to produce either combination or 
decomposition; we have seen how this force modifies the 
chemical molecules either by interposing other molecules, or 
under the influence of physical forces, such as heat and elec- 
tricity. The study of all these phenomena constitutes chem- 
istry, the science of molecular changes ; a science grand in 
purpose and in magnitude, since it penetrates to the very 
nature of the bodies surrounding us ; a science unlimited in 
its applications, since through it we learn to know and control 
the powerful forces which are at work in the most intimate 
structure of matter. 

If we trace the acquired facts to the most obvious and most 
certain conclusion, we must admit the diversity of matter. 
There exists, indeed, a certain number of bodies, each of which, 
when submitted to the various tests resulting from the applica- 
tion of physical and chemical forces, furnishes but one and the 
same substance, and it is impossible to obtain anything else 
than this substance from the body. We maintain, then, until 
proved to the contrary, that each of these bodies contains but 
a single kind of matter, and they are called simple bodies or 
elements. The chemical forces reside, as has been seen, in the 
most remote particles, in the atoms of these bodies. In uniting 
together, the elements form compound bodies, and it has al- 
ready been stated that such combinations result from the juxta- 
position of the atoms which attract each other. The idea of 
atoms is an hypothesis, but the hypothesis is based upon nu- 
merous and important facts, which it weaves together in the 
most natural manner. It is more than an hypothesis : it is a 
theory. Chemists have universally adopted it, for it has ren- 
dered immense service to the science. Let us proceed, then, 
to a consideration of the facts upon which it is based. 



DEFINITE PROPORTIONS, EQUIVALENTS. 



21 




Fig. 5. 



DEFINITE PROPORTIONS, EQUIVALENTS. 

The proportions by weight according to which bodies combine are invaria- 
ble for each combination — These proportions are the equivalents — Ex- 
periments demonstrating this fact. 

Experiment. — A test-glass (Fig. 5) contains a liquid which 
is universally known as sulphuric acid. Although largely di- 
luted with water, that is, 
mixed with a large quan- 
tity of that liquid, it still 
manifests its presence by 
energetic properties. It 
has a very sour and cor- 
rosive taste, — a quality of 
an acid. If a few drops 
of blue litmus solution be 
added to it the blue color 
instantly changes to bright 
red. Another glass contains 
a solution of caustic potash 
or potassium hydrate. This 
substance possesses a strong, lye-like, alkaline taste, very easy 
to distinguish from that of the acid. The color of the blue 
litmus is not aiFected by this liquid, but if a few drops of the 
litmus solution, previously reddened by an acid, be added, the 
blue color is immediately restored. This caustic substance 
has properties which are different from those of acids, and 
which are called basic or alkaline properties. Potassium 
hydrate is an alkali or powerful base. 

If now the alkaline liquid, which has a blue color, be poured 
drop by drop into the acid, which is red, and the mixture be 
stirred with a glass rod, a moment arrives when the red color 
of the acid liquid changes to blue. Exactly at this moment 
we have a solution which has no action uj^on litmus ; it will 
not redden the blue solution, neither will it restore the blue 
color to the red. This may be demonstrated by dipping into 
it first a red and then a blue litmus-paper. Furthermore, this 
liquid possesses neither the acid taste of the oil of vitriol nor 
the alkaline taste of the caustic potash, but its taste is salty. 

By their mixture and reciprocal action the sulphuric acid 
and the potash have lost the energetic properties which they 



22 ELEMENTS OF MODERN CHEMISTRY. 

manifested in the free state. They are exactly saturated ; they 
are neutralized. That is, the liquid which now contains both, 
or more properly the product of their reaction, is neither acid 
nor alkaline ; it is neutral, and its neutrality is manifested both 
by its indiiference to vegetable colors and by its effects on our 
organs of sense. There is no excess, neither of sulphuric acid 
nor of potash, but the two bodies have reacted exactly upon 
each other and have both disappeared, and from their recipro- 
cal action two new bodies result, — a salt called potassium sul- 
phate, and water. 

Whenever sulphuric acid is thus saturated by potash, there 
arrives a moment when the whole of the acid is precisely neu- 
tralized by the alkali, and when the two bodies are converted, 
without residue of either one or the other, into potassium sul- 
phate and water ; and it is always easy to recognize the instant 
at which this effect is produced by the action of the liquid upon 
vegetable colors, such as solution of litmus, or syrup of violets. 
The latter is reddened by an acid, changed to green by an 
alkali, and assumes its natural violet tint when the neutral 
point is reached. Now, it has been found that this last effect 
is only produced when the acid and the alkali are mixed in 
certain proportions, which remain invariable, whatever may be 
the quantities which are mixed. In other words, it has been 
found that the quantities of sulphuric acid and potash which 
reciprocally neutralize each other and form potassium sulphate, 
maintain a constant ratio to each other. It may be easily proved 
that when the state of neutrality has been once attained, it is 
immediately passed and disturbed by the least excess of either 
acid or base that may be added to the liquid. This is made 
evident by the immediate change in the color of the liquid to 
either red or green. 

Thus, in order to form sulphate of potassium with a given 
quantity of sulphuric acid, it is necessary to add an invariable 
quantity of potash ; and if the quantity of sulphuric acid be 
increased by a third, or in any proportion whatever, it is neces- 
sary to increase by a third, or in the same proportion, the quan- 
tity of potash. 

Experiments of this kind have been made with other acids 
and other bases, and have introduced into the science the fun- 
damental notion that these bodies react upon each other in 
definite proportions to form salts, and that consequently the 
composition of the latter bodies is perfectly fixed. A given 



DEFINITE PROPORTIONS, EQUIVALENTS. 23 

quantity of any acid whatever, invariably saturates a fixed 
quantity of the same base. This, then, is the first point. 

It may be added that similar researches made towards the 
close of the last century have led to a not less important result, 
namely, the respective quantities of several acids which satu- 
rate a given weight of one base are exactly proportional to the 
quantities of the same acids which saturate a given weight of 
another base. The law which governs the composition of salts 
was discovered towards the close of the last century by a Ger- 
man chemist, Richter. We cannot now expose it in detail ; 
such development will be better placed and better understood 
in that part of this work which treats of the formation of salts. 
For the present it is sufficient to state that the law mentioned 
is a consequence of the law of definite proportions, and that 
the latter law is universal. It applies not only to the reaction 
of acids upon bases, but is true for all chemical combinations. 
It may be thus expressed : 

The relative iceights according to which bodies combine are 
invariable for each combination. 

There is one feature of the laws which control the composi- 
tion by weight of bodies that it is important to comprehend well. 

It may be best illustrated by experiment : 

100 gr. of mercury are put into the presence of chlorine 
gas, a body possessing very powerful affinities. In this man- 
ner mercuric chloride or corrosive sublimate is formed, and it 
is found that 35.5 gr. of chlorine are necessary to convert 100 
gr. of mercury into this compound. These figures — 100 and 
35.5 — express the invariable ratio in which these elements are 
combined in corrosive sublimate. Here we have the definite 
proportions. 

Now let the 135.5 gr. of corrosive sublimate be dissolved in 
water, and a plate of copper be placed in the solution ; this 
metal will displace the mercury, and combining with the 35.5 
gr. of chlorine will form with it cupric chloride, which will 
remain in solution, coloring the liquid green. The 100 gr. of 
mercury are then precipitated, and it will be found that 31. Y5 
gr. of copper have entered the solution and actually combined 
with 35.5 gr. of chlorine. 

Into this solution of cupric chloride a plate of zinc is now 
plunged ; all of the copper is precipitated in its turn, and 33 
gr. of zinc enter into combination with the 35.5 gr. of chlorine, 
forming zinc chloride. 



24 ELEMENTS OF MODERN CHEMISTRY. 

The 35.5 gr. of chlorine have now been combined success- 
ively with 

100 gr. of mercury, 
31.75 gr. of copper, 
33 gr. of zinc. 

These numbers, w^hich express the respective quantities of 
mercury, copper, and zinc which combine with the same quan- 
tity of chlorine, may be called the equivalents of these metals. 
In fact, these quantities are equivalent to each other in relation 
to the same quantity of chlorine, the experiment having shown 
us that in order to displace 100 gr. of mercury combined with 
35.5 gr. of chlorine it is necessary to employ 31.75 gr. of 
copper or 33 gr. of zinc. 

To continue, 100 gr. of mercury are combined with oxygen, 
and it is found that this quantity of the metal requires 8 gr. of 
oxygen to form the red powder called mercuric oxide. 

But how much oxygen is necessary to form cupric oxide 
with 31.75 gr. of copper? Remarkable as it seems, exactly 
8 gr. are required, and 8 gr. are also requisite to form oxide 
of zinc with 33 gr. of zinc. 

100 gr. of mercury, 
31.75 gr. of copper, 
33 gr. of zinc, 

which are equivalent compared to 35.5 gr. of chlorine, are then 
also equivalent in relation to 8 gr. of oxygen. 

Chlorine itself may be oxidized, and there exists a gaseous 
compound of chlorine and oxygen which contains precisely 8 
gr. of oxygen for 35.5 gr. of chlorine. 

Thus, there are required 

„- J. r vi • 4. /• 1,1 • 1 -j-u r 1^^ gi'- of mercurv, 

35.5 gr of chlorine to f«)rmchlor,dosw.th. . J h, .7! g^. of copper, 
8 gr. of oxygen to oxidize [ 33 gr. of zinc, 

and also 

8 gr. of oxygen to oxidize 35.5 gr. of chlorine. 

In general, if 

A, B, C, combine with D, 

A. B, C,* combine also with E, 

and further, D combines Avith E, 

the letters A, B, C, I), E, representing the weights of the dif- 
ferent elements wdiich enter into combination, or the propor- 
tions according to which the bodies combine among themselves. 



MULTIPLE PROPORTIONS. 25 

They are expressed by numbers that have been called combin- 
ing weights or equivalents ; these represent the ratio of weights 
or the relative weights. They are indeed relative to a unit 
which has served as a term of comparison, and which is the 
equivalent of hydrogen. That is, the quantity of hydrogen 
which combines with 85.5 of chlorine being 1, the equivalent 
quantities of oxygen, zinc, copper, and mercury will be repre- 
sented by the numbers 8—33—31.75—100. 

These are the facts of experiment. Let 33 gr. of zinc be 
treated with hydrochloric acid, the latter is immediately de- 
composed ; its chlorine combines with the zinc, forming chlo- 
ride of zinc, and its hydrogen is disengaged. In this experi- 
ment the hydrogen of the hydrochloric acid is simply displaced 
by the zinc. Now, 33 gr. of this metal will displace exactly 
1 gr. of hydrogen. 

It is seen that the numbers which have been given do not 
express absolute quantities, but merely the relative weights ac- 
cording to which the bodies combine or replace each other in 
compounds, these relative weights being compared to that of 
hydrogen, which is taken as unity. 

Such is the signification of the numbers. 

100 31.75 33 35.5 8 1 

of of of of of of 

mercury, copper, zinc, chlorine, oxygen, hydrogen. 

This being admitted, in order to determine the equivalent 
of an element it is sufficient to find the quantity of that ele- 
ment which combines either with 1 of hydrogen or with a 
quantity of another element which is equivalent to 1 of hydro- 
gen, for instance, 8 of oxygen. 

The notion of equivalents can be understood from the pre- 
ceding considerations ; it appears as a consequence of the law 
of definite proportions ; it comprehends certain facts relative 
to the laws of tlie composition of bodies, but it by no means 
represents the full scope of these laws. The following devel- 
opments add important features. 

MULTIPLE PROPORTIONS. 

Two bodies may combine in several proportions. Thus, 

with oxygen, carbon forms two compounds, both of which are 

gaseous. The less rich in oxygen is carbon monoxide ; the 

richer is carbon dioxide, or carbonic acid gas. Dalton was the 

B 3 



which represent 
the equivalents. 



26 ELEMENTS OF MODERN CHEMISTRY. 

first to perceive that for the same quantity of carbon, carbonic 
acid contains exactly twice as much oxygen as carbon monoxide. 
He made analogous observations concerning the composition 
of two compounds of carbon and hydrogen, the monocarbide 
of hydrogen or marsh gas, and the dicarbide of hydrogen or 
olefiant gas. From these observations he deduced the law of 
multiple proportions, which may be thus stated : when two 
bodies, simple or compound, unite in several proportions to 
form several compounds, the weight of one of these bodies 
being considered as constant, the loeights of the other va,ry 
according to a simple ratio. 

Thus, taking up one of the examples given above, carbon 
unites with oxygen in two proportions : 

Carbon monoxide contains 16 parts of oxygen to 12 parts 
of carbon. 

Carbon dioxide contains 32 parts of oxygen to 12 parts of 
carbon. The numbers 16 and 32 are in the ratio of 1 : 2. 

Nitrogen forms five compounds with oxygen ; if such quan- 
tities of these compounds be taken as contain the same weight 
of nitrogen, the weights of the oxygen will be proportional 
to the numbers 1, 2, 3, 4, 5. 

Nitrogen monoxide contains for 28 parts of nitrogen 16 parts of oxygen. 
Nitrogen dioxide " 28 " " 32 " " 

Nitrogen trioxide " 28 " " 48 " " 

Nitrogen tetroxide " 28 " " 64 " " 

Nitrogen pentoxide '' 28 " " 80 " " 

These numbers, 16, 32, 48, 64, 80, are multiples of the first 
by the numbers 1, 2, 3, 4, 5. 

Five compounds of manganese and oxygen are known, and 
similar relations exist between the quantities of oxygen con- 
tained in these compounds. 

The first contains 55 parts of manganese to 16 of oxygen. 

The second " 55 '* " 24 

The third " 55 « " 32 " 

The fourth " 55 " " 48 " 

The fifth " 55 " " 56 " 

The numbers 16, 24, 32, 48, 56 are in the simple propor- 
tion 1 : 1.5 : 2 : 3 : 3.5. 

Such is the law of multiple proportions discovered by 
Dalton. 

HYPOTHESIS OF ATOMS. 

The brilliant researches of Dalton did not terminate with 
the acquisition ot facts, but sought to account for them by a 



GAY-LUSSAC'S LAWS. — ATOMIC THEORY. 27 

theoretical conception. Taking up the old idea of Lysippus 
and the word of Epicurus, he supposed all ponderable matter 
to be composed of indivisible particles which he called atoms. 
He gave a precise meaning to the vague and ancient notion by 
considering on one hand that the atoms of each kind of matter, 
of each element, possess an invariable weight, and on the other 
that combination between different kinds of matter results from 
the juxtaposition of their atoms. Such is the atomic hypothe- 
sis, the substance of which we have already indicated in treat- 
ing of chemical phenomena in a general manner. It permits 
a simple and rational interpretation of the laws of the compo- 
sition of bodies, and establishes between these laws a firm bond 
of theory. 

Indeed, if the combination of bodies results from the juxta- 
position of their atoms, the latter being considered as indivisi- 
ble and possessing a constant weight for each element, it is 
evident that combination can only take place in definite pro- 
portions, for these proportions represent the invariable relations 
between the weights of the atoms which are in juxtaposition. 
If, on the other hand, one body may combine with another in 
several proportions, such combination can only take place by 
the juxtaposition of 1, 2, 3, 4, etc., atoms of one body with 
one or more atoms of the other. It evidently results that the 
weight of the latter body being constant, the weights of the 
other in these various combinations must be multiples of each 
other. 

An hypothesis which gives such a simple and precise ex- 
planation of the facts relative to definite and multiple propor- 
tions is surely worthy of attention. It acquires still further 
import and becomes elevated to the rank of a theory when to 
these facts are added others entirely different from the first, 
but not less important. 

GAY-LUSSAC'S LAWS.— ATOMIC THEORY. 

Gases combine in simple volumetric proportions — Relations which exist 
between the volumes of gases and their atomic and molecular weights — 
Equal volumes of gases or vapors contain the same number of molecules 
— The molecular weights are equal to double the densities compared to 
hydrogen. 

Among these new facts it is convenient to first notice those 
which were discovered by Gay-Lussac, from 1805 to 1808. 
They relate to the volumes of gases which combine together. 



28 



ELEMENTS OF MODERN CHEMISTRY. 



Experiment. — 10 cubic centimetres of hydrogen and 5 cubic 
centimetres of oxygen are introduced into a tube (Fig. 6), which 

is inverted over the mer- 
cury-trough. The gaseous 
mixture occupies the up- 
per portion of the tube, 
which is an eudiometer. 
Into the upper extremity 
of this tube is hermeti- 
cally cemented a small 
iron wire with a little 
ball at each extremity. 
Another iron wire passes 
through the wall of the 
tube at a short distance 
from the upper extremity, 
in such a manner that the 
interior extremity of this 
second wire is opposite, 
and at a short distance 
from the lower ball of the 
superior and vertical wire. 
A little iron chain is at- 
tached to the exterior end 
of the horizontal wire, and 
dips into the mercury of the trough. Things being thus 
arranged, the inferior extremity of the eudiometer is" closed 
by an iron cap, and the charged plate of an electrophorus is 
approached to the upper button. A spark instantly passes be- 
tween the two buttons in the eudiometer, and a bright flash is 
seen to fill the whole space occupied by the gaseous mixture. 
The combination of the two gases has taken place with the 
development of luminous heat. Water has been formed, and 
is condensed in drops too small to be perceptible. If now the 
eudiometer be opened, by removing the cap which closes it 
under the mercury, the latter at once rises to the top of the 
tube, and fills the whole of the space at first occupied by the 
hydrogen and oxygen. These gases have then combined exactly 
in the proportion of 10 volumes of the first to 5 of the second, 
or more simply, in the proportion of 2 volumes to 1 volume. 

If the eudiometer-tube be now surrounded by a wider glass 
tube, and the latter be filled with oil heated to 120"", the heat 




Fig. 6. 



GAY-LUSSAC'S LAWS. — ATOMIC THEORY. 29 

communicated to the eudiometer will be sufficient to convert 
into steam the water which was condensed, and it may be 
proved, all corrections being made, that the vapor occupies a 
volume equal to exactly 10 cubic centimetres ; that is, a volume 
equal to that of the hydrogen employed. 

From the facts thus established we draw the conclusion that 
2 volumes of hydrogen exactly combine with 1 volume of 
oxygen to form 2 volumes of vapor of water. 

There is thus determined a simple ratio not only between 
the volumes of hydrogen and oxygen which combine, but 
further, between the volume of vapor of water formed and 
the sum of the volumes of the composing gases. 3 volumes 
of the latter are reduced to exactly 2 by the combination. 

Analogous facts have been discovered for other gases, as 
shown by the following examples : 

2 volumes of nitrogen + 1 volume of oxygen z= 2 volumes of nitrogen 

monoxide. 
2 volumes of chlorine + 1 volume of oxygen = 2 volumes of chlorine 

monoxide. 

In other cases the combination of two gases determines a 
still greater contraction, and the initial volume is reduced one- 
half. Thus 

1 volume of nitrogen + 3 volumes of hydrogen = 2 volumes of ammonia 
gas. 

Finally, when two gases combine in equal volumes, their 
combination usually takes place without contraction ; in other 
words, the volume of the gas produced is equal to the sum of 
the volumes of the component gases. 

From these collected facts we may draw the following general 
conclusions : 

1. There is a simple relation between the volumes of gases 
which combine. 

2. There is a simple relation between the sum of the volumes 
of the combining gases and the volume of the gas resulting 
from the combination. 

These laws were first signalized by Gay-Lussac, whose name 
is attached to them. Their importance is immense ; they have 
added a notable development to the atomic theory. 

If the definite proportions by weight in which bodies com- 
bine represent, according to Dalton, the relative weights of 
their atoms, it is natural to conclude that the definite and 
simple proportions by volume in which gases combine, accord- 

3* 



30 



ELEMENTS OF MODERN CHEMISTRY. 



ing to Gay-Lussac, represent the volumes occupied by the 
atoms. Under the same volume gases would then contain 
the same number of atoms. This was first proposed by Am- 
pere, who based his conclusion on the important consideration 
that gases dilate and contract nearly equally when submitted 
to the same variations of temperature and pressure. Within 
certain limits the proposition is true ; it applies to a large num- 
ber of simple gases. But if equal volumes of these gases, 
measured, let it be well understood, under the same conditions 
of temperature and pressure, contain the same number of atoms, 
it is evident that the weights of these equal volumes should 
represent the weights of the atoms. In other words, the 
atomic weights of the simple gases should be proportional to 
their densities. 

The densities of gases and vapors represent the weights of 
these gases or vapors compared to the weight of an equal 
volume of air. To determine the density, a certain volume of 
the given gas is weighed, and this weight is divided by that of 
an equal volume of air, under the same conditions of tempera- 
ture and pressure. The air is then the unit to which are com- 
pared the densities of gaseous bodies. On comparing these 
densities to that of hydrogen,^ which we take as unity, we find 
that the same numbers express almost exactly the densities and 
the atomic weights, the unit to which the densities are com- 
pared, that is, hydrogen, being the same as that to which are 
compared the atomic weights. The figures in the following 
table demonstrate this to be the case : 



Elements. 


Densities of 
Gases or Vapors, 
Air being Unity. 


Densities, 

Hydrogen being 

Unity. 


Atomic 
Weights. 


Hydrogen 

Oxygen 

Nitrogen 

Sulphur (density at 1000°) 

Chlorine 

Bromine 

Iodine 


0.0693 

1.1056 

0.9714 

2.22 

2.44 

5.393 

8.716 


1 

15.9 
14 

32 
35.2 

77.8 
125.8 


1 

16 
14 

32 
35.5 
80 
127 



1 To do this it is sufi&cient to multiply the densities of the gases compared 
to air by = 14.44, which is the density of the air compared to hy- 

drogen as unity. 



GAY-LUSSAC'S LAWS. — ATOMIC THEORY. 31 

It is seen from this table that if the densities of gases be 
compared to hydrogen as unity, just as the weights of their 
atoms are compared to hydrogen as unity, the same figures, or 
very nearly the same figures, express both the densities and 
the atomic weights. We may add that, for all the elements 
taken in the gaseous state, there has been determined between 
the densities referred to hydrogen and the atomic weights, if 
not equality, at least a simple ratio. These remarkable rela- 
tions were pointed out by Gray-Lussac. 

Equal volumes of the simple gases above enumerated con- 
tain the same number of atoms. Two volumes of hydrogen, 
then, contain twice as many atoms as one volume of oxygen ; 
and when these gases combine in the ratio of 2 volumes of the 
first to 1 of the second, we must admit that each atom of oxy- 
gen combines with 2 atoms of hydrogen. We say, then, that 
water is composed of 2 atoms of hydrogen and 1 atom of oxy- 
gen. These three atoms so united constitute the smallest 
quantity of water that can exist in the free state. This is 
called a molecule of water. 

But what volume does this molecule occupy ? The experi- 
ment has shown us. We have seen that 2 volumes of hydro- 
gen, in combining with 1 volume of oxygen, yield 2 volumes 
of vapor of water. One molecule of water in the gaseous state, 
then, occupies 2 volumes, if 1 atom of hydrogen occupy 1 
volume, and if 1 atom of oxygen occupy 1 volume. It is 
seen that the volumes represent the atoms, and the relative 
weights of equal volumes, that is, the densities, represent the 
weights of the atoms. 

Let us now consider another compound gas, — ammonia, — 
composed of hydrogen and nitrogen. A very simple experi- 
ment will show in what proportion the atoms of these elements 
are combined in this gas, and the volume occupied by the 
compound compared with the volumes of its component gases. 

Experiment. — 100 volumes of ammonia gas are introduced 
into a tube inverted upon the mercury-trough (Fig. 7), and 
the walls of which are pierced at the upper end by two plati- 
num wires, between the ends of which a small space is left. 
To these wires are attached the extremities of the two con- 
ducting wires of a Ruhmkorif coil, and the current is passed 
so that a series of electric sparks traverses the ammonia between 
the extremities of the wires in the tube. The gas is imme- 
diately decomposed, and the level of the mercury in the tube 



32 ELEMENTS OF MODERN CHEMISTRY. 

is depressed. When the experiment has terminated it is found 
that the volume of the gas has been doubled. Instead of 100 
volumes, there are now 1^00, the gas being measured under the 
same conditions of temperature and pressure as before. It is 
found, by an analytical process that will be indicated further 
on, that these 200 volumes of gas resulting from the decompo- 




FiG. 7. 

sition of 100 volumes of ammonia are composed of 150 vol- 
umes of hydrogen and 50 volumes of nitrogen. These 150 
volumes of hydrogen and 50 volumes of nitrogen are condensed 
by their union into 100 volumes of ammonia. In other words, 
3 volumes of hydrogen and 1 volume of nitrogen are combined 
together in 2 volumes of ammonia. And as the volumes rep- 
resent atoms, it follows that in ammonia gas 3 atoms of hydro- 
gen are combined with 1 atom of nitrogen. But the quantity of 
ammonia containing 1 atom of nitrogen and 3 atoms of hydro- 
gen is the smallest quantity of ammonia that can exist. It is 
a molecule of ammonia, and this molecule occupies 2 volumeS; 
if 1 atom of nitrogen or 1 atom of hydrogen occupy 1 volume. 

Here, then, is another compound gas, — ammonia, — of which 
the molecule occupies 2 volumes, like that of water. It is the 
same with all the gases. All of the atoms which are combined 
to constitute the molecule of a gas or vapor are so condensed 
that the molecule occupies the same volume as the molecule of 
vapor of water, or the molecule of ammonia. 

\(q may state, then, with the Italian chemist, Avogadro, 
that equal volumes of gases contam the same number of mole- 
cules, and that each of these molecules occupies 2 volumes, 
if 1 atom of hydrogen occupy 1 volume. It follows that 
the weight of 2 volumes of a compound gas represents the 
weight of its molecule, the weight of one volume of hydrogen 



GAY-LUSSAC'S LAWS. — ATOMIC THEORY. 33 

being 1. But the wciglit of 2 volumes of a gas or vapor is 
nothing more than the double of its density compared to hy- 
drogen ; for the density is the weight of 1 volume compared 
with the weight of 1 volume of hydrogen. To find the weight 
of the molecule (the weight of 2 volumes) of a gas or vapor, 
it is then only necessary to multiply its density compared to 
hydrogen (the weight of 1 volume) by 2. 

The densities of gases and vapors are generally referred to 
air as unity. To bring them to the hydrogen standard, they 
are multiplied by the number expressing the relation of the 
density of hydrogen to that of air, which is -o.-oe'g-g- = 14.44. 
The product thus obtained expresses the density compared to 
hydrogen, that is, the weight of 1 volume. To find the weight 
of 2 volumes, or the molecular weight, it is then only necessary 
to multiply the densities compared to air by twice the ratio of 
the density of the air compared to hydrogen, that is, by the 
constant factor, — 

1 2 

2 w OQ go 

^ 0.0693 0.0693 "~ " * 

It is seen that if the atomic weights of certain gases can be 
deduced from a comparison of their densities, this same physi- 
cal notion may also serve for the determination of the molecu- 
lar weights of compound gases. 

The numbers which represent double the densities of gases 
or vapors compared to hydrogen, express also the molecular 
weights of these gases or vapors, that is, the weight of all 
the atoms in the molecule, the weight of one atom of hydrogen 
being 1. 

Considering the examples already given, we may deduce the 
molecular weights of water and of ammonia from the densities 
of steam and ammonia gas. 

The density of vapor of water, determined by Gay Lussac 
is 0.6235. To find the molecular weight of water, it is suffi- 
cient to multiply this figure by 28.88. The product, 18, ex- 
presses the weight of a molecule of water, which is indeed 
composed of 

2 atoms of hydrogen =2 

1 atom of oxygen . . . . . . . =]6 

1 molecule of water =18 

Sir Humphry Davy found for the density of ammonia the 



34 ELEMENTS OF MODERN CHEMISTRY. 

number 0.5901. This being multiplied by 28.88, the product, 
17.04, should represent the weight of one molecule of am- 
monia. Ammonia contains 

3 atoms of hydrogen 3 

1 atom of nitrogen . . . . . . . ' . 14 

1 molecule of ammonia 17 

The discovery of the laws which govern the combination of 
gases by volume has seconded in the most efficacious manner 
the progress of the atomic theory. 

In the first place, it has established a marked distinction be- 
tween the old idea of equivalents and the modern one of atoms. 
The equivalents represented merely the ponderable proportions 
according to which bodies combine ; the atomic weights repre- 
sent the relative weights of the volumes of gases which com- 
bine. The equivalent of hydrogen — unity — expressed merely 
that hydrogen was the unit to which were referred the weights 
of other bodies with which it entered into combination. The 
atomic weight of hydrogen is the weight of one volume of 
hydrogen, taken as unity, and to this unit are referred the 
atomic weights of other bodies. 

In the second place, the discovery of Gray-Lussac has shown 
how the atomic weights of simple bodies and the molecular 
weights of compound bodies can be determined from the den- 
sities of gases and vapors. 

However, this resource would be insufficient in very many 
cases. It only applies to gaseous bodies, or such as can be 
conveniently converted into vapor. Now, there are many sub- 
stances with which this is impossible, and serious difficulties 
would be encountered in the determination of the atomic 
weights of certain elements were it not for another physical 
law, discovered by two French physicists, Dulong and Petit. 
It denotes the relations which exist between the specific heats 
and the atomic weights. 

o 
LAW OF SPECIFIC HEATS. 

It is known that in order to raise the temperatures of differ- 
ent bodies through the same number of thermometric degrees 
very different amounts of heat are required. Thus, one kilo- 
gramme of water requires 30 times more heat than one kilo- 
gramme of mercury to raise its temperature one degree, and 
if the quantity of heat required to raise the temperature of 



LAW OF SPECIFIC HEATS. 



35 



one kilogramme of water one degree be represented by 1, the 
quantity required to raise the same weight of mercury one 
degree will be represented by 0.0333 = gL. This fraction ex- 
presses the specific heat of mercury between and 100°. 

The specific heat of a solid or liquid body is then the amount 
of heat required to raise the temperature of a certain weight of 
the body one degree, the amount required to raise the tempera- 
ture of an equal weight of water one degree being taken as 
unity. 

In 1820, Dulong and Petit discovered the remarkable fact 
that if the figures which express the atomic weights of the 
elements, liquid or solid, be multiplied by those which express 
their specific heats, the product obtained is sensibly constant ; 
in other words, the specific heats of the elements are inversely 
as their atomic weights. It results that if such quantities of 
the elements be taken as represent their atomic weights, the 
amount of heat required to raise the temperature of each one 
degree will be sensibly the same. The law discovered by Du- 
long and Petit may then be expressed, — the atoms of the solid 
elements possess sensihli/ the same specific heats. 

This law permits the deduction of the atomic weights from 
the specific heats. Indeed, it is evident that if the product of 
the specific heats by the atomic weights be a constant, that 
may be called the atomic heat^ dividing this product by the 
specific heat should give the atomic weight. The product 
which represents the atomic heat is 6.4, very nearly, as may be 
seen from the following table : 



Names of the Solid Elements. 


Specific 
Heats. 


Atomic 
Weights. 


Products of the 
Specific Heats 
by the Atomic 

Weights. 
Atomic Heats. 


Sulphur, between and 100° . . 
Selenium 


0.2026 
0762 


32 

79.5 
129 

80 
127 

31 

75 

12 

11 

28 

39.1 


6.483 

6.058 

6.115 

6.744 

6.873 

6.850 

6.105 

5.52 

5.5 

5.66 

6.500 




0.0474 


Bromine, between —78 and —20° 
Iodine, between and 100° . . 
Phosphorus, between + 1 and 30° 


0.0843 
0.0541 
0.1887 
0.0814 


Carbon, diamond, at 600° . . . 
Boron, cr^-stallized, at 600° . . 

Silicon, at 1000° 

Potassium 


0.46 
0.5 
0.202 
0.1695 



36 ELEMENTS OF MODERN CHEMISTRY. 

TABLE.— Continued. 



Names of the Solid Elements. 


Specific 
Heats. 


Atomic 
Weights. 


Products of the 
Specific Heats 
by the Atomic 

Weights. 
Atomic Heats. 


Sodium, between — 34 and + 7° . 


0.2934 
9408 


23 

7 

204 

24 

27 

65 

56 

65.2 
112 

59 

59 
184 

96 
207 
210 

63.5 
122 
118 
200 
108 
197 
197.5 
106.5 
199.2 
104.4 
198 


6.748 
6.586 
6.844 
5.998 
5.786 
6.693 
6.116 
6.230 
6.349 
6.301 
6.424 
6.146 
6.931 
6.499 
6.468 
6.042 
6.193 
6.635 
6.494 
6.157 
6.383 
6.503 
6.315 
6.101 
6.058 
6.452 


Thallium .... ... 


033 'i 5 


Magnesium 

Aluminium 

Manganese 

Iron 


0.2499 
0.2143 
0.1217 
0.0110 


Zinc 


09555 


Cadmium 


05669 


Cobalt 


1068 


Nickel 


1089 


Tungsten 


0.0334 


Molybdenum 

Lead 


0.0722 
0314 


Bismuth 


0308 


Copper .... 


09515 


Antimony 

Tin 

Mercury, between — 77. 5 and — 44° 


0.05077 
0.05623 
0.03247 
0.05701 
0.0324 


Gold 


Platinum 


03293 


Palladium 


0.0593 
0.03063 




0.05803 


Ii'idium 


03259 







Carbon, silicon, and boron have long been regarded as ex- 
ceptions to Dulong and Petit's law. Their siDecific heats had 
been determined at comparatively low temperatures, and the 
products of the numbers obtained by the atomic weights fell 
much below 6.4. These exceptions have disappeared ; the ex- 
periments of M. Weber have shown that the specific heat of 
carbon, silicon, and boron increases with the temperature, and 
that for the first two elements it attains a limit, where it re- 
mains sensibly constant. The figures given in the preceding 
table for these three elements are those of M. Weber, and it is 
seen that on multiplying them by the respective atomic weights 
of carbon, silicon, and boron, values are obtained which are 
sensibly near 6.4. 

It will otherwise be remarked that there are sensible difi"er- 



ISOMORPHISM. — CHEMICAL NOMENCLATURE, ETC. 37 

ences between the numbers expressing the atomic heats of the 
various solid elements, showing that Dulong and Petit's law, 
although true in its generality and striking in its enunciation, 
is not free from certain perturbations which give to it the 
character of an approximate law. It is the same with other 
physical laws, Mariotte's law, for example. 



ISOMORPHISM. 

While considering the atomic theory and the determination 
of the relative weights of the ultimate particles of bodies, we 
cannot pass in silence a discovery which has had a great influ- 
ence upon the development of that theory. It is due to E. 
Mitscherlich, who, in 1819, made known the law of isomor- 
phism. This law may be thus stated : there is such a relation 
between the atomic constitutions of compound bodies belonging 
to the same group and their crystalline form, that " the same 
number of atoms combined in the same manner produce the 
same crystalline form, the latter being independent of the 
chemical nature of the atoms, and determined solely by 
their number and arrangement." The importance of the 
proposition as regards the atomic structure of bodies is self- 
evident. We will reconsider it when treating of the general 
characteristics of salts, but we may remark here that it has 
been of great value in the determination of certain atomic 
weights. Indeed, in some cases considerations of a chemical 
nature cannot decide between two numbers for the atomic 
weight of a given element. The choice is then determined by 
the following considerations : such a value must be attributed 
to the atomic weight that the isomorphous compounds formed 
by the element and by another to which it is analogous, may 
be represented by similar atomic formula. 



CHEMICAL NOMENCLATURE AND NOTATION. 

G-ENERAL Considerations. — Sixty-four substances are now 
known which can be resolved into no simpler forms of matter, 
and which are consequently considered as simple bodies or ele- 
ments. By combining together, they form an innumerable mul- 
titude of compound bodies containing two or more elements. 

4 



38 ELEMENTS OF MODERN CHEMISTRY. 

In order to distinguisli these bodies from each other it is neces- 
sary to give a name to each, for each constitutes a distinct sub- 
stance. 

The names of the simple bodies have been chosen at will, 
and in some cases recall some peculiar property of the sub- 
stances designated. It was formerly the same with compound 
bodies ; there was no definite rule for their nomenclature. 
From this there resulted a great complication of words which 
embarrassed the exposition of ideas, and often for the same sub- 
stance there were a number of synonyms, of which the least 
inconvenience was to uselessly fatigue the memory. Hence 
chemists have felt the necessity of a regular nom"enelature, 
applicable to compound bodies, and capable of indicating their 
composition. Such is the principle of the chemical nomen- 
clature suggested by Gruyton de Morveau, and developed by 
Lavoisier, Berthollet, and Fourcroy. This nomenclature, with 
some modifications, introduced by the progress of the science, 
is still adopted. 

Independently of this language, the rules of which will 
presently be detailed, chemists have adopted a written nota- 
tion which expresses in concise form the atomic constitution 
of compounds. The name of each element is represented by 
a symbol, which also expresses one atom of the substance. 
This symbol is the initial letter of the name of the element, 
or the initial letter with another when the names of two ele- 
ments begin with the same letter. Thus, H represents one 
atom of hydrogen weighing 1 ; represents one atom of 
oxygen weighing 16. By combining these symbols together, 
it is easy to represent in a precise manner the atomic compo- 
sition of compound bodies. From such combinations result 
chemical formulas^ the use of which was introduced into the 
science by Berzelius. 

In the following table will be seen the names of the ele- 
ments now known, together with their atomic weights, and the 
symbols by which the atoms of the elements are represented in 
the notation. 

The greater number of the elements possess certain physi- 
cal properties which characterize them as metals. They are 
opaque, and possess a peculiar lustre, which does not disappear 
under the burnisher. They are good conductors of heat and 
electricity. 



CHEMICAL NOMENCLATURE AND NOTATION. 



39 



Names of the Ele- 
ments. 



(stibi- 



Aluminium 
Antimony 

urn) . 
Arsenic 
Barium 
Bismuth 
Boron . 
Bromine 
Cadmium 
Caesium 
Calcium 
Carbon 
Cerium 
Chlorine 
Chromium 
Cobalt 
Copper 
Didymium 
Erbium 
Fluorine 
Gallium 
Glucinium 
Gold (aurum 
Hydrogen 
Indium . 
Iodine 
Iridium . 
Iron (ferrum) . 
Lanthanium 
Lead (plumbum) 
Lithium . . . 
Magnesium . . 
Manganese . . 



s 


tomic 


^ 


<^ 


Al 


27.5 


Sb 


122 


As 


75 


Ba 


137 


Bi 


210 


Bo 


11 


Br 


80 


Cd 


112 


Cs 


133 


Ca 


40 


C 


12 


Ce 


92 


CI 


35.5 


Cr 


52.5 


Co 


59 


Cu 


63.5 


Di 


96 


Er 


112.6 


Fl 


19 


Ga 


69.9 


Gl 


9.5 


Au 


197 


H 


1 


In 


113.4 


I 


127 


Ir 


198 


Fe 


56 


La 


92 


Pb 


207 


Li 


7 


Mg 


24 


Mn 


55 

1 



Names of the Ele- 
ments. 



Mercury (hydrar 
gyrum) . . 

Molybdenum . 

Nickel . . . 

Niobium . . . 

Nitrogen , . . 

Osmium . . . 

Oxygen . . . 

Palladium . 

Phosphorus . . 

Platinum . . 

Potassium(kalium) 

Rhodium . . , 

Rubidium . , 

Ruthenium . , 

Selenium. . 

Silicon . . 

Silver (argentum) 

Sodium (natrium) 

Strontium . . 

Sulphur . . . 

Tantalium . . 

Tellurium . . 

Thallium . . . 

Thorium . . . 

Tin (stannum) . 

Titanium . . 

Tungsten (wolfi-a 
mium . 

Uranium . . . 

Vanadium . . 

Yttrium . . . 

Zinc .... 

Zirconium . . 



1 
a 


.2 B 


Hg 


200 


Mo 


96 


Ni 


59 


Nb 


94 


N 


14 


Os 


199.2 





16 


Pd 


106.6 


P 


31 


Pt 


197.5 


K 


39.1 


Rh 


104.4 


Rb 


85.2 


Ru 


104.4 


Se 


79.5 


Si 


28 


Ag 

Na 


108 
23 


Sr 


87".5 


S 


32 


Ta 


182 


Te 


128 


Tl 


204 


Th 


234 


Sn 


118 


Ti 


50 


W 


184 


Ur 


120 


V 


51.37 


Y 


89.6 


Zn 


65.2 


z. 


90 



Otlier elements, fewer in number, do not possess these prop- 
erties. They have been called the non-metallic bodies, some- 
times the metalloids. They include the following : 



HYDROGEN. 


OXYGEN. 


NITROGEN. 


BORON. 


SILICON. 




SULPHUR. 


PHOSPHORUS. 




CARBON. 


CHLORINE. 


SELENIUM. 


ARSENIC. 






BROMINE. 


TELLURIUM. 


ANTIMONY. 






IODINE. 




(bismuth?) 






FLUORINE. 











From a theoretic stand-point this distinction presents but 



40 



ELEMENTS OF MODERN CHEMISTRY. 



little value, for it is impossible to draw an exact line sepa- 
rating the metals from the non-metallic bodies. 

Nomenclature of Compound Bodies. — The principle of 
chemical nomenclature is to indicate the composition of com- 
pound bodies by their names. Among such compounds the 
most numerous and the most important are those containing 
oxygen. They are binary or ternary ; that is, the oxygen in 
them is combined with one or two other elements. 

Binary Oxyg^en Compounds. — We will first consider the 
more simple oxidized bodies, those which result from the com- 
bination of oxygen with but one other element, metallic or 
non-metallic. These compounds are called oxides, and differ 
as the element associated with the oxygen is metallic or non- 
metallic. .In combining with non-metallic elements, oxygen 
generally forms compounds which are the anhydrides of acids, 
that is, compounds capable of uniting with water to form 
acids ; with the metals it forms metallic oxides. 

Experiments. — 1. A small piece of phosphorus is placed in- 
a capsule floating on the surface of mercury. It is ignited 
and 'the capsule covered with a bell-jar (Fig. 8). The phos- 
phorus burns, giving off a thick smoke, which condenses in 




Fig. 8. 

white flakes on the sides of the bell-jar. This substance re- 
sults from the combination of the phosphorus with the oxygen 
of the air : it \^ phosphorus pentoxide, ov phosphoric anhydride. 



CHEMICAL NOMENCLATURE AND NOTATION. 41 

2. If lead be heated in the air and maintained for some 
time in a state of fusion, its brilliant surface becomes tarnished 
and covered with grayish particles, which are finally converted 
into a yellow powder. This body is formed by the combina- 
tion of the lead with oxygen : it is plumbic oxide, or oxide of 
lead. 

But, as we have seen, such combination can take place in 
different proportions. An atom of a body may unite with 
1, 2, 3, or more atoms of oxygen, and the names of the com- 
pounds so formed should indicate the degree of oxidation. 

Sulphur forms two compounds with oxygen : one contains 2 
atoms of oxygen to 1 atom of sulphur ; the other, 3 atoms of 
oxygen to 1 of sulphur. They are designated by the names 
sulphuro?(s oxide, or anhydride, and sulphur/c oxide, or anhy- 
dride. 

The written notation represents them by the symbols 

SOI 

so^ 

which express their atomic compositions. The number of 
atoms of any element is indicated by a small figure placed after 
and a little above or below the symbol of that element. 

The degree of oxidation is then expressed by the termina- 
tion in ous or ic of the name of the other element, which 
indicates the kind of oxide, ic denoting the superior oxide. 

Mercury forms two compounds with oxygen. The first 
contains 2 atoms of mercury for 1 of oxygen ; the second, 1 
atom of mercury to 1 of oxygen. They are designated by the 
names and symbols as follows : 

Mercurous oxide Hg'-^O. 

Mercuric oxide HgO. 

The names monoxide, sesquioxide, dioxide, etc., as will be 
seen further on, are also employed.^ 

A monoxide is a combination of 1 atom of metal with 1 atom of oxygen. 
A sesquioxide " " 2 atoms " " .3 atoms " 

A dioxide " " 1 atom " " 2 " <' 

It is easy then to understand the signification of the follow- 
ing names and symbols : 

1 The prefixes proto, hi or dent, and fer have been, and are yet, frequently 
employed instead of mono, di, and tri. 

4-- 



42 ELEMENTS OF MODERN CHEMISTRY. 

Manganese monoxide MnO. 

Manganese sesquioxide Mn'^^O^. 

Manganese dioxide MnO"-. 

The oxide most rich in oxygen is sometimes called the per- 
oxide. 

Oxygen Acids and Metallic Hydrates. — The oxygen com- 
pounds that we have just considered may unite with the ele- 
ments of water to form more complex compounds, which are 
ternary, that is, they contain three elements. To the two ele- 
ments of the oxide is then added a third, independently of the 
oxygen of the water, that is, its hydrogen. 

The oxygen acids usually result from the union of water 
with the non-metallic oxides. 

Experiment. — Sulphur trioxide or sulphuric anhydride 
occurs in white silky tufts. It is very volatile, and if a bottle 
containing it be opened, its vapor comes in contact with the 
moist air and forms thick white fumes. If a small quantity of 
this substance be thrown into water, it immediately disappears 
and combines with that liquid. So great is the energy of the 
reaction that the heat disengaged gives rise to the production 
of steam, which, being suddenly formed and condensed in the 
midst of the cooler liquid mass, causes a peculiar noise, a sort of 
hissing. When the sulphuric oxide is dissolved in the water, 
the solution presents a very acid reaction. It contains sulphuric 
acid, the compound long known under the name of oil of vitriol. 

This reaction may be represented in the abbreviated lan- 
guage of the notation, which expresses the atomic composition 
of bodies with so much precision. The formula of sulphuric 
anhydride or sulphur trioxide is 

SO^ 
that of water is 

Then if sulphuric acid result from the addition of all of the 
elements of water to those of sulphuric trioxide, it should contain 

SO^ + H^O = H^SO^ 

This is a chemical equation^ and it is seen that the two 
terms of the first member express the atomic composition of 
the reacting bodies, while the single term of the second mem- 
ber gives the atomic composition of the product of the reac- 
tion.- Such an equation accounts for all of the atoms, and 



CHEMICAL NOMENCLATURE AND NOTATION. 43 

the sum of all of the atoms written in the first member must 
exactly balance the sum of all those written in the second. 

There is a compound known as nitric anhydride, or nitrogen 
pentoxide. It results from the combination of nitrogen with 
oxygen, and its atomic composition is represented by the 
formula N^O^ In combining with water it forms nitric acid. 

N^O^ + H'^0 = 2(HNO^0- 

Nitric anhydride. Water. Nitric acid. 

(1 molecule.) (2 molecules.) 

These examples, which could be indefinitely multiplied, give 
an idea of the constitution of the ternary oxygen acids. The 
rules which have been already given for the nomenclature of 
the oxides apply also to the nomenclature of the acids. We 
have phosphorous acid and phosphoric acid. .£^j90-phosphor- 
ous acid is an acid of phosphorus containing still less oxygen 
than phosphorous acid. {Hi/po^ literally, under.) 

The metallic hydrates result from the combination of water 
with the metallic oxides. It is well known that when quick- 
lime is sprinkled with water it becomes heated, increases in 
volume, cracks into pieces, and is finally converted into a white, 
impalpable powder, which constitutes slaked lime, — a com- 
pound of the lime with water. Lime is the oxide of a metal 
called calcium. In combining with water it forms a ternary 
compound of calcium, hydrogen, and oxygen ; this is hydrate 
of calcium, or, as it is commonly called, hydrate of lime. 

CaO + H^O = CaH^Ol 

Calcium oxide. Water. Calcium hydrate. 

(Lime.) 

The metal potassium, the radical of potash, forms with oxy- 
gen a compound which contains two atoms of potassium com- 
bined with one atom of oxygen. The composition of this body 
is then represented by the formula K^O. 

It combines with water with great energy, and forms with it 
potassium hydrate or caustic potassa. 

K^O + H^O --^ 2K0H. 

Potassium oxide. Water. Potassium hydrate. 

(2 molecules.) 

Oxygen Salts. — The oxygen salts result from the action of 
the oxygen acids upon the oxides or upon the metallic hydrates. 

Experiment. — The formation of a salt may be illustrated by 
a modification of one of the experiments already described. 

A quantity of dilute nitric acid is slightly reddened by a so- 



44 ELEMENTS OF MODERN CHEMISTRY. 

lution of blue litmus or syrup of violets.^ Some dilute solution 
of caustic potassa is also treated with the same coloring matter ; 
the syrup of violets will assume a green color, or blue litmus 
will remain unchanged. 

The latter liquid, which is alkaline, is now added drop by 
drop to the acid, until the red color disappears, giving place to 
the violet color of the syrup of violets or the blue of the litmus. 
The liquid is now neutral. It contains neither free nitric acid 
nor free potassa. Both have disappeared as such ; they are 
reciprocally neutralized, the first having lost its acid taste, the 
second its extreme caustic properties. They have produced a 
body having a saline, cooling taste, and exerting no action upon 
vegetable colors. It is a neutral salt which has been formed. 
It is called potassium nitrate. It is the nitre or saltpetre of 
the ancient chemists. It is not, however, the sole product of 
the reaction. Water is formed at the same time, and if we 
would comprehend the entire phenomenon, the reaction will be 
expressed by the following equation : 

HNO^ + KOH = KNO^ + H^O. 

Nitric acid. Potassium hydrate. Potassium ultrate. Water. 

It is seen that the salt, potassium nitrate, is a ternary com- 
pound, similar in constitution to nitric acid itself On com- 
paring the two formulas, 

HNO' nitric acid, 
KNO^ potassium nitrate, 

it is seen that they only differ by the K in the second occupy- 
ing the place held by the H in the first. It may then be said 
that potassium nitrate represents in a manner nitric acid in 
which the hydrogen has been replaced by an equivalent quan- 
tity of potassium. This definition applies to the entire class 
of compounds under consideration. A salt represents an acid 
of which the hydrogen has been wholly or partially replaced 
by an equivalent quantity of metal. 

The acids constitute the salts of hydrogen : they are neu- 
tralized when this hydrogen is replaced by a metal. The acid 
or hydrogen salt differs from the metallic salt. From a theoretic 
point of view, an acid is a compound of the same order as a 
salt, and if these bodies are separated by such great differences 

^ An infusion of common purple cabbage may be substituted for syrup 
of violets. 



CHEMICAL NOMENCLATURE AND NOTATION. 45 

of properties, this is due to the nature of the base. What 
a difference, indeed, between hydrogen gas and the metals ! 

We have studied the formation of a salt by the action of an acid, 
nitric acid, upon a metallic hydrate, potassium hydrate. The 
anhydrous oxides may also form salts by reacting with the acids. 

Experimient. — Yellow oxide of lead, when digested with 
dilute sulphuric acid, is converted into a white, insoluble pow- 
der, which is lead sulphate. This is a salt, but it is not the only 
product of the reaction, for water is formed at the same time. 
H^SO* + PbO = PbSO* + H^O. 

Sulphuric acid. Lead oxide. Lead sulphate. Water. 

Lastly, among other modes of formation of salts, there is one 
which is worthy of interest, and of which an idea may be ob- 
tained from the following example. 

Sulphur trioxide, or sulphuric anhydride, combines energetic- 
ally with barium oxide or baryta, and from the union of all of 
the elements of both compounds there results a salt, — barium 
sulphate. 

SO' + BaO = BaO,SO' or BaSO*. 

Sulphur trioxide. Barium oxide. Barium sulphate. 

But, whether this salt be formed under these conditions, or 
by the action of sulphuric acid, its composition only differs 
from that of the latter acid by the substitution of Ba for H^ 
H^SO* sulphuric acid, hydrogen sulphate, 
BaSO* barium sulphate. 

The reactions which we have just studied, and which indicate 
the principal methods of the formation of salts, are sufficient to 
make clear the definition before given, that salts are derived from 
acids by the substitution of a metal for hydrogen. The nomen- 
clature defines and preserves these relations. To distinguish the 
different salts of the same acid, the name of the metal is placed 
first, and this is followed by the name of the acid, which is but 
slightly changed, — ic is changed to ate^ and ou8 to ite. 

Thus Sulphuric acid 
Nitric acid 
Perchloric acid 
Sulphurous acid 
Hyposulphurous acid 

These generic names follow the names of the metals which 
enter into the composition of the salts, and which specify them, 
as it were. Thus, we have : 



gives 


1 sulphates, 
nitrates. 


il 


perchlorates. 

sulphites. 

hyposulphites. 



46 ELEMENTS OF MODERN CHEMISTRY. 

Potassium sulphate, copper sulphate, lead sulphate, etc. ; 

Sodium sulphite ; 

Potassium nitrate, barium nitrate, silver nitrate, etc. 

But we know that a single metal may form several com- 
pounds with oxygen. In reacting upon the same acid these 
different oxides give rise to the formation of different salts. 

Thus, two different sulphates of copper are obtained, as sul- 
phuric acid is caused to react with cuprous oxide, or with 
cupric oxide. 

H^'SO* + Cu^O == Cu^SO* -f- H^O. 

Sulphuric acid. Cuprous oxide. Cuprous sulphate. Water. 

H'^SO* H- CuO = CuSO* + H^O. 

Cupric oxide. Cupric sulphate. 

It is easy to distinguish these two salts from each other by 
using the adjectives cuprous and cupric before the substantive 
sulphate. Thus, we have mercurozts and mercuric sulphates ; 
ferroifs and ferric sulphates. 

The preceding considerations will give an idea, sufficient for 
the time being, of the constitution and the nomenclature of 
salts. Their further exposition will be completed farther on. 

Nomenclature of Non-Oxygenized Compounds. — The non- 
metallic elements other than oxygen can combine among them- 
selves or with the metals. Such compounds are designated by 
the name of one of the elements followed by the abbreviated 
name of the other terminating in ide. Thus, the compounds 
of the metals with chlorine, bromine, iodine, sulphur, arsenic, 
and carbon are called chloriV^es, bromu?es, iod/cfc-s, sulph/ci^e.?, 
arsen^Hes, carbic?es. We thus have sodium chloride, potassium 
bromide, lead iodide, zinc arsenide, iron carbide. The termi- 
nation iiret was formerly used in place of ide. 

But a non-metallic body, such as chlorine or sulphur, can, 
like oxygen, form several compounds with the same metal. In 
these compounds 1 atom of metal may be united with 1 or 2 
atoms of sulphur, or with 1, 3, or 5 atoms of chlorine, or again 
with 2 or 4 atoms of chlorine. Such atomic composition is 
expressed by the following names and symbols : 

Iron ??ic>;)osulphide FeS. 

Iron (bisulphide FeS'^. 

Phosphorus trichloride ......... PCl^. 

Phosphorus /)ej(<ach]oride ........ PCl^. 

Tin (6'chloride • . SnCl^. 

Tin ieimchloride SnCi*. 

Antimony /r/chloride SbCP. 

Antimony pcH^ochloride SbCl^. 



CHEMICAL NOMENCLATURE AND NOTATION. 47 

The names thus express precisely the number of atoms of 
the second element in combination with 1 atom of the first. 

The compounds of chlorine, bromine, iodine, and several 
other elements with hydrogen are acids ; they readily exchange 
their hydrogen for a metal, so forming compounds that are 
analogous to the oxygen salts, and which constitute the haloid 
salts of Berzelius. 

Experiment. — The compound of chlorine with hydrogen is 
hydrochloric acid ; it is a gas, and dissolves in water, forming 
a fuming, strongly-acid liquid. When it is carefully poured 
into a concentrated solution of caustic potassa there appears a 
white precipitate, formed of little crystals and presenting the 
appearance of a salt. This is potassium chloride. It is formed 
according to the following reaction, and its formation is at- 
tended by the production of heat : 

HCl + KOH = KCl + H^O. 

Hydrochloric Potassium Potassium Water, 

acid. hydrate. chloride. 

The hydrogen compounds of bromine, iodine, fluorine, sul- 
phur, etc., possess analogous properties. They are called 

Hydrobromic acid HBr. 

Ilydriodic acid HI. 

Hydrofluoric acid HFl. 

Sulphydric acid or sulphuretted hydrogen , . . H-^S. 

The chlorides may combine among themselves. It is the 
same with the bromides, iodides, sulphides, etc. If a solution 
of potassium chloride be poured into a concentrated solution 
of platinic chloride, a yellow precipitate, constituting a com- 
pound of the two chlorides, is formed. It is the double chlo- 
ride of platinum and potassium, or potassium platino-chloride. 

There exist, likewise, double sulphides formed by the union 
of two simple sulphides. Such compounds constitute what are 
called sulphur salts. 

Alloys and Amalgams. — The compounds of the metals 
with each other are called alloys. Amalgams are the alloys 
of mercury, that is, the compounds of this liquid metal with 
another metal. 



48 



ELEMENTS OF MODERN CHEMISTRY. 



HYDROGEN. 

Density compared to air 0.0693. 

Atomic weight (1 volume taken as unity) H = 1. 

This body was discovered in 1766 by Cavendisli. It is one 
of the elements of water, hence its name, which was given by 
Lavoisier. 

Experiments. — 1. A small piece of sodium is passed under a 
tube filled with mercury and inverted 
on the mercury-trough ; it rises to 
the top of the jar, and some water 
is then introduced (Fig. 9). As soon 
as the water touches the sodium a 
brisk disengagement of gas is ob- 
served ; this is hydrogen, produced by 
the decomposition of the water, and 
the reaction by which it is set at 
liberty is expressed in the following 
equation : 

2H^0 + Na^ = 2NaOH 

Water. Sodium. Sodium 

hydrate. 

If the tube be now inverted and a lighted taper be rapidly 
brought to the orifice, the gas will burn with a pale flame. A 
piece of reddened litmus-paper plunged into the water con- 
tained in the tube has its blue color at once restored, and 
this change is produced by the sodium hydrate or caustic soda 
dissolved in the water. 

2. Some thin sheet-zinc cut into small pieces is introduced 
into a rather large test-jar (Fig. 10), and some hydrochloric 
acid is then poured upon it. A rapid effervescence imme- 
diately takes place, and if a lighted taper be brought to the 
mouth of the jar, the stream of hydrogen evolved takes fire. 
This hydrogen is produced by the decomposition of the hydro- 
chloric acid by the zinc, which is converted into chloride. 




- W. 

Hydrogen. 



2HC1 -f 


Zn = 


= ZnCP 


+ HI 


Hydrochloric 

acid. 
(2 molecules.) 


Zinc. 


Zinc 
chloride. 


Hydrogen 



HYDROGEN. 



49 



Preparation. — A reaction analogous to the preceding is 
turned to advantage for the preparation of large quantities of 
hydrogen. Dilute 

sulphuric acid is de- 
composed by zinc. 

A two-necked bot- 
tle is about half filled 
with water, and gran- 
ulated zinc, or sheet- 
zinc cut into small 
pieces, is introduced; 
sulphuric acid is then 
added in small quan- 
tities by the aid of 
a funnel-tube which 
dips under the surface 
of the water (Fig. 
11). The reaction at 
once commences, and 
hydrogen is disen- 
gaged. When the 
air at first contained 
in the bottle has been 
entirely expelled, the 
gas may be collected 
in jars or bottles filled 
with water and in- 
verted on the pneu- 
matic trough. 

In this reaction the zinc disappears and dissolves in the 
liquid with evolution of heat, and it often happens, if the liquid 
be sufiiciently concentrated, that colorless crystals of zinc 
sulphate are formed on cooling. This salt and hydrogen are 
the sole products of the reaction of pure zinc upon sulphuric 
acid largely diluted with water. 

H^SO* + Zn r= ZnSO* -f W, 

Sulphuric acid. Zinc. Zinc sulphate. Hydrogen. 

Physical Properties, — Hydrogen is a colorless gas, and 
when pure has neither taste nor odor. It is the lightest of all 
known bodies, its density compared to air being 0.0693 ; that 
is, if one volume of air weigh 1, one volume of hydrogen, 
measured under the same conditions of temperature and pres- 




50 



ELEMENTS OF MODERN CHEMISTRY. 



sure, weighs only 0.0693. Hydrogen is then 14.44 time 
lighter than air. The weight of one litre of hydrogen at 0° 




FiG. 11. 

and under the normal pressure is 0.0895 gramme. Instead 
of comparing the densities of gases and vapors to that of air, 
it is preferable to compare them to that of hydrogen taken as 
unity (page 30). 

Hydrogen passes with great facility through vegetable and 
animal membranes, and through porous substances that are im- 
pervious to water. It cannot be kept in a glass vessel that 
presents the least crack, for it would pass through much more 
readily than air. This property is expressed by saying that hy- 
drogen is very diffusible. According to Magnus, it is the only 
gas gifted with an appreciable conductibility for heat ; in this 
respect it is related to the metals. From a consideration of its 
physical properties and its combined chemical properties, Fara- 
day long ago announced the metallic character of hydrogen. 

This theoretic prediction has recently received a remarkable 
confirmation. Hydrogen, which was long regarded as incoerci- 
ble, has been liquefied and even solidified. Caillete't, of Paris, 
obtained it in the form of a cloud by exposing it to a pressure 
of 300 atmospheres at a temperature of — 29° and then sud- 
denly relieving the pressure. Raoul Pictet, of Gleneva, has 
advanced still further. By an apparatus of incomparable 
power, he subjected it to a temperature of — 140° under a 
pressure of 650 atmospheres. Under these circumstances, hy- 
drogen was liquefied, and was visible as a steel-blue, liquid jet 



HYDROGEN. ' 51 

at the moment of its projection from tlie tube in which it was 
condensed. The cold produced by its passage from the liquid 
to the gaseous state was so great that a portion of the liquid was 
solidified, and fell to the ground in metallic grains, producing 
a shrill sound as it struck the floor. Another portion of the 
solidified hydrogen remained in the tube during several minutes. 

Among the physical properties of hydrogen may be men- 
tioned the remarkable faculty it possesses of passing through 
plates of iron or platinum at high temperatures (H. Sainte- 
Claire Deville and Troost). It is well known that it rapidly 
passes through thin sheets of caoutchouc. According to 
Graham, this property is related to that possessed by certain 
solid bodies, and particularly metals, such as iron, platinum, 
and palladium, of absorbing hydrogen gas. This chemist 
designated the phenomenon by the name, occlusion of hydro- 
gen by the metals. Palladium especially is distinguished by 
the energy with which it ab'sorbs hydrogen. It can condense 
in its pores nine hundred times its own volume of the gas. A 
palladium wire may be charged with hydrogen by arranging it in 
a voltameter so that it constitutes the negative pole of a small 
battery, the positive pole being a stout platinum wire. When 
the current passes, the hydrogen set at liberty at the negative 
pole (see page 71) is condensed in the palladium. This metal 
undergoes at the same time a remarkable change. Its volume 
augments and its density diminishes, but its metallic lustre 
remains, as do also, to a certain degree, its tenacity and con- 
ductibility for electricity; besides this it becomes magnetic. 
There is thus formed a sort of alloy of palladium and hydro- 
gen, containing about 20 volumes of palladium to 1 volume of 
hydrogen reduced to the solid state. The density of this solid 
hydrogen compared to that of water, according to the determi- 
nations of Troost and Hautefeuille, is 0.62 : it is a little greater 
than that of lithium. Graham insisted upon the metallic char- 
acter of hydrogen thus alloyed with palladium, and proposed 
for it the name liydrogenmm. 

Chemical Properties. — Hydrogen is a combustible gas, and 
the product of its combustion is water. 

Experiments. — 1. A lighted taper may be thrust into a rather 
wide tube filled with hydrogen (Fig. 14). The gas takes fire 
on contact with the flame, but the taper is extinguished in the 
atmosphere of hydrogen. It may be relighted by withdrawing 
it through the burning gas. The experiment shows at the 



52 



ELEMENTS OF MODERN CHEMISTRY. 



same time that hydrogen is inflammable and that it is incapa- 
ble of supporting combustion itself. 

2. A gas-bottle, A (Fig. 12), is arranged for the preparation 
of hydrogen, and water, zinc, and sulphuric acid are intro- 




FiG. 12. 

duced. The hydrogen evolved is made to traverse the tube 
CB, which is filled with fragments of chloride of calcium ; after 
having been dried by this substance, which is very avid of 

water, the gas escapes by the tube 
a, the end of which is drawn out 
to a point. The jet of gas is 
lighted, and burns with a pale 
flame. A bell-jar, D, is now 
held over the burning jet, and 
the sides of the glass soon be- 
come covered with dew, the 
drops of which unite and run 
down to the edge of the jar. This 
is water, and it is formed by the 
combustion of the hydrogen ; that 
is, by its combination with the 
oxygen of the air. 

3. A jet of hydrogen may be 
lighted by holding in it a tuft of 
asbestos which has been dipped 
in platinum black, that is, finely-divided platinum. The con- 
densation of the hydrogen in the pores of the finely-divided 
metal is so rapid that the platinum becomes heated to redness, 
and then ignites the gas. 




Fig. 13. 



HYDROGEN. 



53 



4. A tube filled with hydrogen may be held in the vertical 
position, bottom upwards, without the gas escaping rapidly by 
the inferior opening. If the tube be inclined, the hydrogen 
overflows and escapes upwards through the air. It may then 
be received in a second tube held vertically above the first, 
which is inclined more and more (Fig. 13). The passage of 
the gas into the upper tube can be demonstrated by approach- 
ing to the latter a lighted taper, when the hydrogen will burn 
with a faint explosion. 

Before igniting or collecting hydrogen escaping from a gen- 
erator, it should always be ascertained that the whole of the air 
has been expelled, otherwise dangerous explosions may result. 

5. The explosions may take place with the production of a 
harmonious sound, if they are made to succeed each other 





Fig. 14. 



Fig. 15. 



rapidly and at regular intervals. These conditions are realized 
by burning a small jet of hydrogen in a somewhat large tube 
(Fig. 15). The flame is drawn away from the jet by the draft 
in the tube, but immediately recedes as the ascending hydro- 



54 



ELEMENTS OF MODERN CHEMISTRY. 



gen gas mixes with the air, at the same time producing a faint 
explosion, and the rapid succession of these explosions produces 
a musical tone. 

The hydrogen condensed in palladium appears to have some 
chemical properties diiferent from those of gaseous hydrogen 
(Grraham). It combines in the dark and at ordinary tempera- 
tures with iodine and chlorine ; the direct union of ordinary 
hydrogen with iodine is impossible, and with chlorine it takes 
place at the common temperature only under the influence of 
light. It seems, then, that hydrogen, when associated with 
palladium, is more active than in the ordinary state. 



OXYGEN. 

Density compared to air . ....... 1.1066. 

Density compared to hydrogen 16. 

Atomic weight =16. 

Oxygen was discovered, in 1774, by Priestley, who obtained 

it by heating red 
precipitate or 
mercuric oxide. 

Experim ent. — 
A tube, a (Fig. 
16), contains a 
concentrated so- 
lution of the dis- 
infecting powder 
known as chlo- 
ride of lime ; a 
small quantity 
of the peroxide 
of cobalt, a com- 
pound of oxygen 
with the metal 
cobalt, is then 
introduced, and 
the whole is gen- 
tly heated. A 
brisk eiferves- 
ip^Q 2(3 cence takes place, 

and if a match 
which has been just blown out and still presents a spark of fire 




OXYGEN. 55 

be thrust into the mouth of the tube, it is instantly relighted, 
and burns with great brilliancy. This effect is due to a gas 
which is being disengaged, and which, to use the expression of 
Lavoisier, is eminently fitted to support combustion. 

It is the gas to which that great chemist gave the name 
oxygen. It is produced by a very simple reaction. Under 
the influence of the peroxide of cobalt, the calcium hypochlorite 
which is contained in the chloride of lime is converted into 
calcium chloride and oxygen. 

CaCPO^ = CaCP + 01 

Calcium hypochlorite. Calcium chloride. Oxygen. 

Preparation. — Large quantities of oxygen may be prepared 
by a process analogous to the preceding. When potassium 
chlorate is heated, it is converted into potassium chloride, and 
gives up all of its oxygen. To facilitate this decomposition, a 
small quantity of manganese dioxide is mixed with the chlo- 
rate. The part taken by the manganese dioxide is analogous 
to that of the cobalt peroxide in the preceding reaction, and is 
not thoroughly understood ; it is most probable that it serves 
to distribute the heat more regularly through the mass of 
chlorate. If the temperature be sufficiently elevated, the de- 
composition of the chlorate is complete, and takes place accord- 
ing to the following equation : 

KC10=^ = KCl + 01 

Potassium chlorate. Potassium chloride. Oxygen. 

The operation may be conducted in a glass retort, which 
should be about one-third filled with the mixture of chlorate 
and dioxide ; to the beak of the retort is adapted a delivery- 
tube, which dips under the surface of the water or mercury in 
the trough (Fig. 17). The retort is then heated by an alco- 
hol or gas lamp, and the chlorate melts and disengages its oxy- 
gen with effervescence. Towards the close of the operation, 
the heat is increased in order to decompose into potassium 
chloride and oxygen any potassium perchlorate that may have 
been formed by the union of a portion of the evolved oxygen 
with some of the chlorate. 

To make larger quantities of oxygen for filling the gas- 
holders of laboratories, etc., a mixture of potassium chlorate 
and manganese dioxide is heated in a sheet-iron or copper retort. 

At a bright red heat manganese dioxide gives up a third 



56 



ELEMENTS OF MODERN CHEMISTRY. 



of its oxygen, and is converted into the red oxide of manga- 
nese. 

3MnO' = Mn^O* + 0\ 

Manganese dioxide. Red oxide of manganese. Oxygen. 

Oxygen can be cheaply manufactured on the large scale by 
the process of Tessie du Mottay. This depends upon the for- 
mation of sodium manganate by the action of air upon a heated 




Fig. 17. 

mixture of manganese dioxide and caustic soda, and the subse- 
quent decomposition of this manganate at about 450° by a 
current of steam, a decomposition which again sets at liberty 
the oxygen absorbed by the manganese dioxide to form sodium 
manganate. The operation is continuous. 

Physical Properties. — Oxygen is a colorless, odorless, taste- 
less gas ; it is a little heavier than the air. If one volume of 
hydrogen weighs 1, the same volume of oxygen, measured 
under the same conditions of temperature and pressure, weighs 
16. This is expressed by saying that the density of oxygen 
compared to that of hydrogen is 16. A litre of oxygen weighs 
1.437 gr. at 0° and under the normal pressure. 

Until lately oxygen had been considered as a permanent gas. 
By subjecting it to a pressure of 300 atmospheres and a tem- 
perature of —29°, and then suddenly relieving the pressure, 
Cailletet obtained it in the form of a cloud. Raoul Pictet 
liquefied it by a pressure of 300 atmospheres and a temperature 



OXYGEN. 



57 



of — 140°. He attributes to liquid oxygen a density near that 
of water,— about 0.9787. 

Oxygen is but slightly soluble in water. A litre of water 
dissolves 0.041 litre, or 41 cubic centimetres, at 0° ; 0.032 litre 
at 10° ; 0.028 litre at 20°. The fractions 0.041, 0.032, 0.028, 
represent the coefficients of soluhility of oxygen in water at 
the temperatures of 0°, 10°, and 20°. 

Chemical Properties. — Oxygen combines directly with most 
of the other elements, and the union often takes place with 
such energy that there results a great evolution of luminous 
heat : it gives rise to the phenomenon of combustion. 

Experiments. — A cone of charcoal of which the point is red- 
hot is plunged into a globe filled with oxygen (Fig. 18), and 
immediately combustion takes place with great brilliancy. The 
oxygen combines with the carbon, forming a colorless gas, which 
is carbonic acid gas. 

In like manner, sulphur and phosphorus burn in oxygen, the 
first producing a colorless, irritating gas known as sulphurous 





Fig. 18. 



Fig. 19. 



acid gas, the second emitting thick fumes, which condense in 
white flakes of phosphoric oxide. 

A watch-spring may be drawn out into a spiral, and a small 
piece of tinder attached to one end ; after igniting the tinder, 
the spiral is rapidly plunged into a bell-jar filled with oxygen, 
and resting upon a plate containing a layer of water (Fig. 19). 
The tinder burns energetically, and heats the end of the spiral 
to redness ; then the combustion of the iron itself commences, 
and goes on with unparalleled brilliancy, and a production of 



58 ELEMENTS OF MODERN CHEMISTRY. 

heat so intense that the oxide of iron formed melts and falls 
in incandescent drops, which fuse themselves into the sur- 
face of the plate, even after having traversed the layer of 
water. 

In the same manner, the combustion of the metal magnesium 
may be effected in oxygen ; it takes place with dazzling splen- 
dor, and gives rise to the production of a white powder, which 
is magnesia, or magnesium oxide. 

The preceding experiments are examples of rapid combus- 
tion. We have seen that solid substances, such as charcoal, 
iron, and magnesium, become incandescent in combining with 
oxygen : it is the phenomenon of fire. We have also seen that 
vapors, like those of sulphur and phosphorus, become lumi- 
nous in their combination with oxygen : this is the phenome- 
non of flame. 

But fire and flame are not necessary concomitants of the 
union of bodies with oxygen. It is true that such union is 
always accompanied by the production of heat ; but often this 
heat is not luminous ; sometimes it is imperceptible to our 
senses. 

Thus iron, the combination of which with oxygen at a red 
heat gives rise to such a brilliant combustion, may unite with 
this gas at ordinary temperatures under the influence of 
moisture. There is thus formed ferric hydrate, which consti- 
tutes rust. 

This oxidation of the iron, which takes place slowly, pro- 
duces a feeble disengagement of heat, which is, however, imme- 
diately dissipated. Such phenomena of oxidation are designated 
by the name sloiv combustion. 

The term combustion would then be synonymous with oxi- 
dation did we not know, on the other hand, that all chemical 
combination gives rise to the production of heat. If copper 
be thrown into boiling sulphur, a vivid incandescence is pro- 
duced, due to the union of the two bodies. Likewise antimony 
and arsenic, when projected in fine powder into an atmosphere 
of chlorine, unite with the latter body, producing a brilliant 
combustion. It is seen that in these cases the production of 
luminous heat indicates an euGrgetic combination, but not an 
oxidation. 

Oxygen is one of the elements of the air ; it is the cause 
and the agent of all combustion, of all oxidation which takes 
place in our atmosphere ; and the oxygen fixes itself upon 



OXYGEN. 59 

burning bodies in such a manner that the product of the com- 
bustion contains all of the matter of the combustible body and 
all of the matter of the oxygen. This is one of the fundamental 
truths of chemistry, and for its discovery not less than a cen- 
tury and a half of work was required. The glory of the dis- 
covery belongs to Lavoisier. 

His researches on combustion revealed to him the true 
nature of the phenomena of respiration. The Respiration of 
animals is a slow combustion ; it is the source of animal heat. 
It gives rise to the formation of carbonic acid gas and water, 
products of the complete oxidation through which must pass 
those organic matters in the economy which no longer serve 
the purposes of life, and all of which contain carbon and hy- 
drogen. 

The production of carbonic acid gas by the act of respira- 
tion is easy to prove. It is only necessary to blow, by the aid 
of a tube, the air contained in the lungs through clear lime- 
water, which soon becomes milky from the formation of insolu- 
ble carbonate of lime. 

An annular jet of hydrogen through which a jet of oxygen 
is forced constitutes what is known as the oxyhydrogen blow- 
pipe, and is one of the most intense sources of heat known. 
Platinum melts before it like wax, and iron and other combus- 
tible metals burn brilliantly when introduced into its flame. 
The flame of the oxyhydrogen blowpipe gives but little light, 
but when it is projected upon a piece of lime, the latter becomes 
heated to dazzling incandescence, constituting the Drummond 
or calcium light. 

OZONE, OR OXYGEN PEROXIDE. 

002. 

The repeated discharges of a good electric machine develop 
a peculiar odor. This is due to the production of a body which 
was discovered by Schonbein in 1840, and which he named 
ozone (from oC^y, I smell). 

Experiment: — Some potassium permanganate is mixed with 
barium dioxide in a mortar, the mixture transferred to a flask, 
and moistened with sulphuric acid. The characteristic odor of 
ozone immediately becomes perceptible, and a moistened paper, 
impregnated with potassium iodide and starch and held in the 



60 



ELEMENTS OF MODERN CHEMISTRY 



neck of the flask, immediately assumes a blue color.^ This effect 
is caused by the ozone evolved. 

This remarkable body is also formed under the following 
circumstances. 

1. By the passage of electric sparks through oxygen. — It is 
sufficient to pass a series of electric sparks through oxygen 

contained in a tube above a solu- 
tion of iodide of potassium and 
starch, in order to produce the 
blue color caused by the ozone 
(Fig. 20). 

It has been noticed that the 
largest quantity of ozone is pro- 
duced when the passage of the 
electricity through oxygen is ef- 
fected, not by sparks, but by non- 
luminous or obscure discharges 
(Andrews and Tait, de Babo). 
I)ry and pure oxygen can be con- 
verted into ozone in this manner. 
But this conversion only takes 
place partially, the ozone formed 
remaining mixed with a large 
excess of oxygen. A contraction 
takes place at the moment the 
■pjQ 20 oxygen is transformed into ozone. 

These experiments prove that 
ozone is condensed oxygen (Andrews and Tait, de Babo, Soret). 

2. By the electrolysis of water. — When acidulated water 
is decomposed by the battery current, the oxygen which is 
disengaged at the positive pole contains small quantities of 
ozone, and the proportion of the latter may be increased by 
adding a considerable quantity of sulphuric or chromic acid to 
the water. 

3. During slow oxidation. 




-Some sticks of cleanly-scraped 



1 Such a paper is called ozonoscopic. It is colored blue by the combina- 
tion of the starch with the iodine set at liberty by the OKone. According 
to Houzeau, it is preferable to use a delicate, wine-colored litmus-paper, 
one-half of which is impregnated with potassium iodide. Ozone will change 
the color of this half to blue, for, in decomposing the potassium iodide, it 
forms potassium hydrate, and this restores the blue color to the litmus. 
Under these conditions, the other half of the paper undergoes no change 
in color, while it would be colored red by acid vapors, or blue by ammonia. 



OZONE. 



61 



phosphorus are introduced into a bottle containing enough 
water to just about half immerse them, and the whole is agi- 
tated from time to time. In a short time the air in the bottle 
will be charged with a small quantity of ozone. 

According to Schonbein, who observed these facts, ozone is 
produced during all slow combustions. Thus, when oil of tur- 
pentine is exposed to the air under the influence of sunlight, 
it is slowly oxidized, and in becoming resinified, it becomes at 
the same time charged with a small quantity of ozone, which 
dissolves in it. 

4. By the decomposition of barium dioxide hy sulphuric 
acid. — This decomposition gives rise to barium sulphate and 
oxygen charged with a small quantity of ozone (Houzeau). 



H^SO* -f BaO' 



BaSO* + H^O + 



The barium dioxide is introduced in small portions into sul- 
phuric acid contained in a flask, to the neck of which is fitted 
a glass stopper pierced for the passage of the delivery-tube, 
which is ground in (Fig. 21). 




Properties of Ozone. — Ozone possesses an intense and pecu- 
liar odor. At a temperature of 290° it is reconverted into 
ordinary oxygen, the volume of which is greater than that 
occupied by the ozone. It is then certainly condensed oxygen. 
It has energetic oxidizing properties ; it even oxidizes bodies 
which possess only feeble affinities for oxygen. In the presence 
of alkalies it combines with nitrogen, converting it into nitric 
acid, which combines with the alkali. 

It oxidizes silver at ordinary temperatures, converting it into 



62 ELEMENTS OF MODERN CHEMISTRY. 

the dioxide Ag^O^. It instantly decomposes potassium iodide, 
setting free the iodine. It is insoluble in water, but is entirely 
soluble in oil of turpentine and oil of cinnamon, both of which 
it slowly oxidizes. It oxidizes and destroys the greater number 
of organic substances. In most of these oxidations only a third 
part of the oxygen contained in ozone is active ; the other two- 
thirds become free in the form of ordinary oxygen, so that the 
volume of the latter set free is exactly equal to that primitively 
occupied by the ozone. 

Hence it is concluded that 3 volumes of oxygen are con- 
densed into 2 volumes by their conversion into ozone, and if 
ordinary oxygen be the oxide of oxygen 00, ozone will be oxy- 
gen peroxide OO'^ (Odling). 

00 = 2 volumes of oxygen. 


00"* or / \ =2 volumes of ozone. 

0—0 

This conclusion of Odling's concerning the nature of ozone, 
has been verified by the determination of the density of this 
body. Soret has established that when ozone diluted with oxy- 
gen is absorbed by oil of turpentine or oil of cinnamon, there 
is a diminution of volume sensibly double the increase of 
volume noticed on subjecting the same gas to the action of 
heat. He naturally concludes that the density of ozone is one 
and a half times that of oxygen, or 1.658. These figures have 
been confirmed by direct experiments upon the rapidity of 
diffusion of ozone. It has been shown by the researches of 
Grraham that when diffusion between two gases takes place 
through an opening, without the interposition of a diaphragm, 
the rapidity of diffusion is inversely as the square roots of the 
densities of the gases. Soret has demonstrated that the 
rapidity of diffusion of ozone is notably greater than that of 
chlorine, and very near but somewhat less than that of car- 
bonic acid. It results that its density is less than that of 
chlorine, and a little greater than that of carbonic acid, which 
is 1.525 ; this confirms the density 1.658. 

An important property of ozone is its reduction by hydrogen 
dioxide, and the simultaneous decomposition of the latter com- 
pound. The products are ordinary oxygen and water. 

00^ + HW = 2(00) + H^O 

Ozone. Hydrogen dioxide. Ordinary oxygon. Water. 



THE ATMOSPHERE. 



63 



ATMOSPHERIC AIR. 

The air is a mixture of oxygen and nitrogen. It also con- 
tains traces of carbonic acid gas and a variable proportion of 
vapor of water. 

Its composition was established by Lavoisier by an experi- 
ment that has become celebrated. Having heated mercury in 
a limited quantity of air to a temperature near its boiling-point 
for several days, he observed the formation of a red powder, a 
combination of the mercury with oxygen. On the termination 
of the experiment, he found that the volume of the air had 
diminished about one-sixth. He carefully collected the oxide 
formed, introduced it into a small retort, and heated it to red- 
ness. He thus obtained a gas " eminently qualified to support 
combustion and respiration," and the volume of which was 
sensibly equal to that of the gas that had disappeared. This 
gas he named oxygen. He mixed it with the irrespirable resi- 
due from the first experiment, which would not support com- 
bustion, and so reconstituted atmospheric air. The composition 
of the latter was thus established by analysis and synthesis. 
This experiment was infinitely more instructive than that 
undertaken by Scheele at about the same time. The great 
Swedish chemist only absorbed the oxygen of the air by the 
alkaline sulphides. The nitro- 
gen remained as residue, but 
the oxygen combined with the 
sulphide could not be again 
separated. 

However, neither one nor 
the other of these methods 
could give the exact propor- 
tion according to which the 
oxygen and nitrogen are mixed 
in the atmosphere. This has 
been deduced from the follow- 
ing experiments. 

Experiments. — 1. Into a small bent tube closed at the 
upper end, filled with mercury and inverted in a vessel of the 
same metal, are passed 100 volumes of air (Fig. 22). A 
small piece of phosphorus is then introduced and brought 
into the upper limb, where it is heated by the aid of a spirit- 
lamp. It takes fire, and in burning consumes all of the 




64: 



ELEMENTS OF MODERN CHEMISTRY. 



oxygen of the 100 volumes of air. The operation has termi- 
nated when the flame of the phosphorus vapor has extended 
down to the cohimn of mercury. The residual gas is then 

allowed to cool, and on being measured is found to be 

reduced to 79 volumes. It is nitrogen. 

2. The absorption of oxygen by phosphorus will take 
place in the cold, if a long stick of this substance be in- 
troduced into a determined volume of air contained in a 
graduated tube. The experiment requires several hours, 
and gives the same result as the preceding. 

3. 100 volumes of air are measured into a graduated 
tube on the mercury-trough. A concentrated solution 
of potassium hydrate is introduced, and then some pyro- 
gallic acid, a white, crystalline substance employed in 
photography; the whole is then rapidly agitated, the 
extremity of the tube being closed by the thumb. 

The alkaline solution is immediately blackened by the 
destruction of the pyrogallic acid. All of the oxygen is 
rapidly absorbed, and when the tube is opened, under 
the surface of the mercury, the 100 volumes of air are 
found reduced to about 79 volumes. 



« 




FiQ. 23. 



Fig. 24. 



4. There is another method capable of still greater precision : 
Fig. 23 represents a Bunsen's eudiometer ; it is a stout glass 
tube about 60 centimetres long and 2 centimetres in diameter. 
Two platinum wires ar.e hermetically sealed into the upper ex- 
tremity through the whole thickness of the glass. Each ter- 



THE ATMOSPHERE. 65 

minates exteriorly in a small loop, and on the interior follows 
the curve of the end nearly to the centre, so as to leave an 
interval of about 1 centimetre between the extremities of the 
two wires. The tube is graduated in millimetres, and the ca- 
pacity of each division is known. It is filled with mercury and 
inverted upon a small trough, 100 volumes of air and 100 
volumes of hydrogen are then introduced. One of the plati- 
num loops is then put into communication with an electrical 
conductor, and the other with the earth, and a spark is passed 
through the mixture (Fig. 24). A flash appears in the tube, 
and all of the oxygen of the 100 volumes of air has combined 
with hydrogen to form water. There thus results a vacuum, 
which is filled by the mercury, and in place of 200 volumes of 
gas introduced into the eudiometer, we find, all corrections being 
made, only 137.21 volumes of a mixture of hydrogen and 
nitrogen. 

62.79 volumes have then disappeared to form water, and 
this water contains all of the oxygen contained in 100 volumes 
of air ; as each volume of this oxygen must consume 2 vol- 
umes of hydrogen, it follows that the 62.79 volumes which 
have disappeared must have contained 20.93 volumes of 
oxygen and 41.86 volumes of hydrogen. 

Hence the 100 volumes of air introduced into the eudiom- 
eter contained 20.93 volumes of oxygen and 79.07 volumes of 
nitrogen. 

Such is the composition of the air by volume. As nitrogen 
is lighter than oxygen, these volumetric relations do not express 
the composition of the air by weight. This was determined 
very exactly by Dumas and Boussingault in the following 
manner. 

A globe, A (Fig. 25), having a capacity of 15 or 20 litres, 
and fitted with a brass cap and stop-cock, R", by which it may 
be connected with an air-pump, is joined to a hard glass tube, 
BB', having a stop-cock at each end, R and R', and filled with 
metallic copper. The air is exhausted from the globe and tube, 
and the weight of each is then accurately determined. 

The tube BB' is placed in a combustion-furnace, and by its 
extremity B' is connected with the tubes K, I, H, Gr, F, E, D, 
C. The tube with bulbs C contains a solution of caustic ^^o- 
tassa ; the tubes D and E are filled with pumice-stone impreg- 
nated with caustic potassa, and the tubes F and Gr with frag- 
ments of solid caustic potassa ; the bulbs H contain sulphuric 

6* 



66 



ELEMENTS OF MODERN CHEMISTRY. 



acid, and the last tubes, I and K, are filled with fragments of 
pumice-stone saturated with sulphuric acid. The potassa serves 

to remove from the air 
the small quantity of 
carbonic acid gas which 
it contains, and the sul- 
phuric acid absorbs the 
moisture. 

The tube filled with 
copper is now heated to 
redness, its stop-cocks 
being open, and the 
stop-cock of the globe is 
gradually opened. Air 
immediately enters, but 
it is first obliged to tra- 
verse the series of tubes, 
where it is deprived 
of its carbonic acid 
gas and vapor of water, 
and also the tube filled 
with incandescent cop- 
per, which absorbs the 
oxygen. It is then pure 
nitrogen which enters 
the globe. The experi- 
ment has terminated 
when the tension of the 
gas in the globe is equal 
to the exterior pressure, 
that is, when no more 
air enters. The stop- 
cock R" is now closed. 
The tube and globe are 
allowed to cool, and are 
weighed separately. 
The increase in weight 

■ of the globe gives the 

■ weight of the nitrogen 
which has entered. 

The increase in weight of the tube, which was first weighed 
exhausted of air, gives the weight of the oxygen which has 




THE ATMOSPHERE. 67 

combined with the copper, plus the weight of the nitrogen 
remaining in the tube at the close of the experiment. The 
weight of this nitrogen is determined by exhausting the tube 
and weighing a third time. The difference between the second 
and third weighings indicates the weight of the nitrogen re- 
maining in the tube at the end of the experiment, and this 
weight added to that of the nitrogen contained in the globe 
constitutes the total weight of nitrogen in the air analyzed. 

The weight of the oxygen is given by the difference between 
the third and first weighings of the tube. 

By this method Dumas and Boussingault found that 100 
parts of air contain by weight 

Oxygen 23.13 

Nitrogen 76.87 

These two gases are simply mixed in the air ; they do not 
exist there in a state of combination ; and the proportions of 
the mixture are universally the same with very slight varia- 
tions. At the summits of the highest mountains, at the centres 
of the continents, and over the vast expanse of the seas, the 
air has been shown to be nearly equally rich in oxygen. From 
a comparison of a great number of analyses, Regnault has es- 
tablished that as a rule the percentage of oxygen only varies 
from 20.9 to 21.0 ; air which has been collected on the open 
sea and close to the surface of the water, has been found to 
contain a somewhat smaller amount (20.6), a circumstance 
which may be attributed to the dissolving action of the water. 

Nitrogen and oxygen are by far the most abundant con- 
stituents of the atmosphere ; among the substances which are 
contained in small proportion must be mentioned particularly 
carbonic acid gas and vapor of water. 

Carbonic Acid Gas and Vapor of Water. — If lime-water 
be poured into a flat dish and exposed to the air, in a few 
hours its surface will be found covered with a white pellicle 
formed of little crystals of calcium carbonate. 

This experiment demonstrates the presence of carbonic acid 
gas in the atmosphere. The watery vapor may be condensed 
by exposing to the air a glass vessel containing a mixture of ice 
and salt. The sides of the vessel soon become covered with a 
layer of frost, resulting from the solidification of the water which 
has been condensed from the air by the cool surfjice of the glass. 

The exact quantities of carbonic acid gas and vapor of water 



68 ELEMENTS OF MODERN CHEMISTRY. 

contained in the air may be determined by drawing the latter 
through tubes containing sulphuric acid and caustic potassa. 
The aspiration is obtained by means of a bottle or a tin vessel, 
y (Fig. 26), filled with water. On opening the stop-cock r, 




Fig. 26. 



the water runs out, and air is drawn in through the tubes F 
and E, filled with fragments of pumice-stone wetted with sul- 
phuric acid, then through D and C, containing pumice-stone 
impregnated with caustic potassa, and finally B, which is like 
the first two. These tubes increase in weight from the absorp- 
tion of vapor of water in the first two, and carbonic acid in 
the others. The diiference in weight of the tubes F and E 
before and after the experiment gives the proportion of con- 
densed water ; the difference of D, C, and B gives the propor- 
tion of carbonic acid gas. The volume of air is equal to that 
of the water which has run out of the aspirator. 

According to the experiments of Theodore de Saussure, the 
quantity of carbonic acid gas contained in the air varies from 
4 to 6 ten-thousandths. It is increased in inhabited places. 
It is greater at night than during the day, a circumstance that 
must be attributed to the influence of vegetation. It is dimin- 



THE ATMOSPHERE. 



69 



ished after a rain, and is found in its minimum proportion 
above tlie surface of large lakes. 

The sources of this carbonic acid gas are various. In cer- 
tain regions fissures in the earth disengage large volumes ; vol- 
canoes emit immense quantities ; certain spring waters are 
supersaturated, and disengage it in abundance when they reach 
the surface of the earth. But the greater portion is produced 
by the phenomena of combustion which take place on the 
earth's surface ; and among these phenomena must be included 
respiration, which is a slow combustion. 

Experiment. — If by the aid of a glass tube, a (Fig. 27), air 
from the lungs be blown through lime-water, the latter becomes 
clouded, by the formation 
of calcium carbonate. The 
carbonic acid gas thus 
fixed by the lime comes 
from the respiration, which 
is an abundant source of 
that gas. 

Does carbonic acid gas 
accumulate indefinitely in 
the atmosphere ? No. Re- 
jected and excreted by ani- 
mals, it serves for the res- 
piration of plants. The 
green parts of vegetables 
possess the power of de- 
composing this gas under 
the influence of the sun's 
light. The carbon is fixed, ^lo, "11. 

and serves for the nu- 
trition of the plant; the oxygen is rejected, if not wholly, at 
least in great part. This truth is one of the most important 
achievements of the science of the last century. It is due to 
the successive labors of Priestley, Bonnet, Ingenhouz, Senne- 
bier, and Theodore de Saussure. 

Independently of carbonic acid gas and vapor of water, air 
contains other matters mixed with or suspended in it in very 
small quantities. Among these must be mentioned : 

1. Traces of ammonia, or rather of ammonium carbonate. 
These substances are dissolved by rain-water, and play an 
important part in vegetation. 




70 ELEMENTS OP MODERN CHEMISTRY. 

2. A trace of hydrogen carbide (Boussingault). 

3. A small quantity of nitric acid in the form of ammonium 
nitrate. It is supposed that nitric acid is formed in the air by 
the direct union of the nitrogen and oxygen under the influ- 
ence of atmospheric electricity. Schonbein asserts that the 
air contains traces of ammonium nitrite : 

(NH^)NO^ 

4. A body which possesses the property of imparting a blue 
color to papers saturated with starch and potassium iodide. 
It is held, and not without reason, that this substance is ozone. 
The phenomenon would also be caused by the presence of 
traces of nitrous vapors or chlorine in the air ; but Andrews 
has shown that air contains a principle which decomposes po- 
tassium iodide, and loses this property when it is brought to a 
high temperature. This fact can be explained if the air con- 
tain ozone, which is destroyed by heat ; it cannot be explained 
if it contain chlorine or nitrous vapors. Besides, the air con- 
tains only very slight traces of ozone, which vary greatly; 
often none is present. The relative proportion of ozone pres- 
ent is approximately estimated by the greater or less intensity 
of the blue color produced upon ozonoscopic paper. 

5. Solid particles suspended in the air and carried to a dis- 
tance by the winds. In perfectly calm air these corpuscles are 
deposited, forming a dust of which the composition is very 
variable. It contains various microscopic vegetable and animal 
germs (Pasteur). 



WATER. 



Vapor density compared to air 0.623. 

Vapor density compared to hydrogen ' ... 9. 
Molecular weight H20 = 18.2 

Water is the product of the combination of hydrogen and 
oxygen ; its composition was established by Lavoisier in 1785. 

1 The density of vapor of water compared to that of hydrogen is 9 ; that 
is, if the weight of 1 volume of hydrogen be represented by 1, the weight 
of 1 volume of vapor of water will be 9 ; in other words, vapor of water is 
nine times more dense than hydrogen under the same conditions of tem- 
perature and pressure. 

■■^ The weight of the molecule or the molecular weight expresses the 
weight of 2 volumes of vapor, if the weight of 1 volume of hydrogen be 
represented by 1. 



WATER. 



n 



The combination takes place exactly in the ratio of 2 volumes 
of hydrogen to 1 volume of oxygen, as demonstrated by the 
following experiments. 

1. Analysis of Water hy Electrolysis. — Water slightly acid- 
ulated with sulphuric acid is introduced into the vessel C 
(Fig. 28), through 
the bottom of which 
rise two platinum 
wires. These wires 

are hermetically i'' 

sealed in the walls 
of the glass, and the 
free exterior ex- 
tremities are con- 
nected with the 
poles of a galvanic 
battery. The cur- 
rent passing through 
the acidulated liquid 
decomposes the 

water,^ and bubbles 

of gas are formed and rapidly rise from the two platinum wires 
which constitute the poles. If two small tubes filled with 
water be inverted over these wires, the gases may be collected, 
aud it will be found that the gas disengaged at the negative 
pole is sensibly double in volume that disengaged at the posi- 
tive. The first is hydrogen, and the second oxygen, and the 
proportion in which these gases are set free would be exactly 
that of 2 to 1, were it not that a small quantity of oxygen re- 
mains dissolved in the acid liquid, or, under certain condi- 
tions, combines with a portion of the water surrounding the 
negative pole to form a trace of hydrogen dioxide, as will be 
mentioned farther on. 

This experiment of the decomposition of water by the pile 
was made for the first time, in 1801, by two English physi- 
cists, Nicholson and Carlisle. 




1 Under these conditions, it is really the sulphuric acid which is decom- 
posed : IPSO* breaks up into H^, which is liberated at the negative pole, 
and SO*, which separates at the positive pole, and is at once decomposed 
into SO^ and 0. The is disengaged, and the SO-^ in the presence of the 
water becomes again hydrated, reforming sulphuric acid. SO^ + H^O = 
H^SO*. The electrolytic action is thus confined to the sulphuric acid, 
which alone is decomposed. 



^2 ELEMENTS OF MODERN CHEMISTRY. 

2. Eudiometric Synthesis. — The composition of water can 
be established by synthesis., that is, by the combination of the 
two elements, hydrogen and oxygen. The experiment, which 
is made in an eudiometer, has already been described (page 28). 
It demonstrates that the two gases combine in the exact ratio 
of 2 volumes of the first to 1 of the second, and that these 
3 volumes of gas are condensed into 2 volumes of vapor of 
water. 

These experiments establish the volumetric composition of 
water ; its composition by weight can be deduced from them, 
the densities of hydrogen and oxygen being known ; for the 
weighable matter of 2 volumes of hydrogen being added to the 
weighable matter of 1 volume of oxygen, it is only necessary 
to add twice the weight of 1 volume of hydrogen to the weight 
of 1 volume of oxygen in order to determine the weight of 2 
volumes of vapor of water. That is to say, the ratio by weight 
in which hydrogen combines with oxygen to form water is that 
of double the density of hydrogen (the weight of 2 volumes of 
H) to the density of oxygen (the weight of 1 volume of 0). 
This ratio is 

2 X 0.06 93 _ 0.1386 _ 1 
1.1056~~ ~ 1.1066 "~ 8 

It may be deduced in a more .simple manner by a com- 
parison of the densities of hydrogen and oxygen. If 1 volume 
of hydrogen weighs 1, 1 volume of oxygen weighs 16 ; the 
weight of 2 volumes of hydrogen will then be 2, and it will be 
seen that the two gases unite, by weight, in the ratio of 

2 _l 

16^8 

18 grammes of water then contain 16 grammes of oxygen 
and 2 grammes of hydrogen. This composition, which can be 
determined only in an approximative manner by a compari- 
son of the densities, owing to the difficulties in the methods 
of weighing gases, has been established in the most rigorous 
manner by Dumas, in an experiment which has become classic, 
and will now be described. 

3. Synthesis of Water by the Gravimetric Method. — In order 
to determine the composition of water by synthesis it is suffi- 
cient to combine an indeterminate quantity of hydrogen with 
a precisely determined weight of oxygen, and to weigh exactly 
the water formed. By subtracting from this latter weight that 



WATER. 



73 



of the oxygen contained in the water, the weight of the hydro- 
gen which has com- 
bined with that oxy- 
gen is obtained. 

In order to thus 
combine hydrogen 



with 



oxygen, it is 




convenient to make 
the former gas react 
upon an oxidized 
body which will read- 
ily yield its oxygen 
to the combustible 
gas. Cupric oxide, or 
black oxide of cop- 
per, CuO, first sug- 
gested by Gay-Lus- 
sac, and employed for 
this purpose by Ber- 
zelius and Dulong, 
fulfils these condi- 
tions. Although un- 
decomposable by heat 
alone, it is readily re- 
duced by hydrogen 
when heated in an at- 
mosphere of that gas. 
Dumas employed the 
apparatus represent- 
ed in Fig. 29. 

Hydrogen is pre- 
pared by the action 
of dilute sulphuric 
acid upon zinc, and 
is purified by being 
conducted through a 
series of U tubes, the 
first containing frag- 
ments of glass wet 
with a solution of lead 
acetate, the second, 
fragments of glass wet with a solution of silver sulphate, and 
D 7 



74 ELEMENTS OF MODERN CHEMISTRY. 

the third, pumice-stone, impregnated with caustic potassa. 
The lead acetate retains hydrogen sulphide ; the silver sulphate 
absorbs hydrogen arsenide, and the potassa absorbs any traces 
of carbides of hydrogen. 

The hydrogen thus purified is dried by passage through an- 
other series of U tubes, the first containing calcium chloride, 
and the others pumice-stone saturated with sulphuric acid. The 
latter tubes are cooled by being surrounded with ice. The gas 
is lastly passed through a smaller tube containing phosphoric 
oxide. The weight of this tube must remain constant during 
the whole of the experiment. It is called the witness-tube. 

The pure and dry hydrogen now passes through a green 
glass bulb, which contains pure cupric oxide. The weight of 
this bulb, together with the oxide which it contains, is deter- 
mined with care. The receiver B', as well as the U tubes 
which terminate the apparatus, are also accurately weighed. 

When the whole of the air contained in the apparatus has 
been expelled by the hydrogen, the flask is heated and the 
cupric oxide is reduced. Water is formed and is in great part 
condensed in the liquid state in the receiver, but a portion of 
the vapor remains uncondensed and is carried off by the excess 
of hydrogen. This vapor is retained in the second series of 
U tubes, which contain calcium chloride and pumice-stone satu- 
rated with sulphuric acid. When the reduction has almost 
terminated, the bulb is allowed to cool, the current of hydro- 
gen being continued ; this gas is finally displaced by a current 
of air, and the weighings are then made. 

The weight of the bulb has decreased by that of all of the 
oxygen which has been taken from the oxide of copper by the 
hydrogen, and which now exists in the water formed. 

The weight of the receiver and the condensing apparatus con- 
nected with it is increased by the weight of all the water formed. 

By subtracting the weight of the oxygen from that of the 
water we find the weight of the hydrogen. 

By the aid of this rigorous method Dumas has found that 
100 parts by weight of water contain 

Hj'drogen 11.11 

Oxygen 88.89 

ioo.oo 
These numbers are in the exact ratio of 

Hydrogen 1 

Oxygen 8 



WATER. 75 

Physical Properties. — Pure water has neither taste nor 
odor. It is Hmpid and colorless. It occurs in three states in 
nature ; during the colds of winter it is solid. Ice, snow, frost, 
sleet, and hail are the different forms which it assumes in this 
state. The temperature at which ice melts is one of the stand- 
ard points in the thermometric scale. To this temperature 
corresponds the of the centigrade scale, which is adopted in 
this work. 

Snow is composed of an agglomeration of little crystals ; 
these are hexagonal prisms, which often present the forms rep- 
resented in Fig. 30. 




Fig. 30. 

At the moment of freezing, water expands, and its density 
is then less than that which it possesses in the liquid state. 
The density of ice is 0.93. Water contracts in volume from 
to -|- 4°, and presents its maximum density at the latter tem- 
perature. Its density at this point is chosen as the unit of 
comparison for the densities of solid and liquid bodies. 

Water and even ice are continually emitting invisible vapors 
which mix with the air, and are, as it were, dissolved in it. 
This vaporization takes place more actively as the temperature 
is raised. 

The air is said to be saturated with vapor at any given tem- 
perature when it refuses to take up any more vapor at that 
temperature. Under these conditions, if the temperature be 
lowered, a portion of the vapor is condensed in fine drops, 
which remain suspended in the air in the form of mist or visi- 
ble vapor. The point at which the moisture of the air is con- 
densed is called the dew-point. 

Water begins to boil when its vapor acquires sufficient ten- 
sion to overcome the atmospheric pressure. This is the boil- 
ing-point, and under a pressure of 0.760 metre corresponds to 
100° of the centigrade scale. 



V6 



ELEMENTS OP MODERN CHEMISTRY. 



Chemical Properties. — Water is partially decomposed by 
the highest temperatures at our command. On pouring melted 
platinum into an iron mortar containing water, Grove observed 
a disengagement of bubbles composed of an explosive mixture 
of oxygen and hydrogen. According to H. Sainte-Claire De- 
ville, vapor of water undergoes a partial decomposition, which 
he calls dissociation, when exposed to a temperature between 
1100 and 1200°. In order to collect the gases resulting from 
this decomposition it is necessary to separate them before they 
have reached a part of the apparatus where a less elevated 
temperature would permit their recombination. For this pur- 
pose Deville directed a current of steam through a porous clay 
tube, a (Fig. 31), surrounded by a tube of glazed porcelain, &, 




Fig. 31. 



which was heated to whiteness in a powerful furnace. A cur- 
rent of carbonic acid gas was passed through the annular space 
between the two tubes, by means of the tube c. The vapor of 
water was decomposed by the heat into hydrogen and oxygen ; 
but these two gases separated from each other : the hydrogen, 
being the more diffusible, passed in great part through the 
porous tube, while the oxygen was delivered by the interior 
tube, together with a small quantity of carbonic acid gas, which 
entered by diffusion. The gases evolved by the two tubes were 
collected in a small jar filled with a solution of caustic potassa 
by which the carbonic acid gas was absorbed, and there re- 
mained an explosive mixture of hydrogen and oxygen. 

Water is decomposed by an electric current, as already seen. 



WATER. 77 

It is likewise decomposed by many of the elements, metallic 
and non-metallic, which combine with one or the other of its 
component elements. Thus, chlorine decomposes it at a red 
heat, uniting with the hydrogen to form hydrochloric acid, and 
setting free the oxygen ; also under the influence of light at 
ordinary temperatures. A number of the metals decompose 
water, liberating the hydrogen. 

Iron decomposes it at a red heat, taking up the oxygen and 
setting free the hydrogen ; potassium and sodium, as we have 
seen in the case of the latter metal, produce the same effect at 
ordinary temperatures. 

Many compound bodies seize upon the elements of water, 
and are decomposed by it. Such are the chlorides of phos- 
phorus and antimony. In these reactions, which will be 
studied farther on, the hydrogen of the decomposed water 
unites with the chlorine, the oxygen with the other element. 

We have already noticed the action of water upon the non- 
metallic and metallic oxides. It combines with many of these 
compounds, forming either acids or metallic hydrates. 

Certain of these reactions aue worthy of reconsideration. It 
is especially important to fully appreciate the part played by 
the water which enters into them. 

When potassium oxide becomes hydrated to form caustic 
potassa, the reaction takes place by a double decomposition, 
which may be expressed by the following equation : 

(1)|}0 + g}o = |}o + ^}o 

Potassium oxide. Water. Potassium hydrate. Potassium hydrate. 

It will be seen that both the potassium oxide and the water 
are converted into potassium hydrate by the exchange of an 
atom of potassium for an atom of hydrogen. Potassium hydrate 
is, as it were, derived from water by the substitution of an atom 
of potassium for an atom of hydrogen. This substitution takes 
place directly when water is decomposed by potassium. 

(2) 2H^0 -\- K^= 2K0H -f H^ 

The potassium hydrate in its turn may lose the remaining 
atom of hydrogen ; if it be heated with potassium, this hydro- 
gen is displaced, and potassium oxide is formed. 



(3) 2K0H + K^ = 


. 2K^0 + H-^ 


Potassium hydrate. Potassium. 


Potassium oxide. Hydrogen. 


7* 





78 ELEMENTS OP MODERN CHEMISTRY. 

It will be seen from what precedes that, starting with water, 
we may form potassium hydrate (2), potassium oxide (3), and 
this again may be converted into potassium hydrate (1). The 
three compounds are then closely related. Each contains 1 
atom of oxygen combined with 2 atoms of another body, hy- 
drogen or potassium, and the relation is clearly expressed in 
the followine: formulae : 



'& 



hIo h^o 



l}o 



Water. Potassium hydrate. Potassium oxide. 

If hypochlorous oxide, Cl'^O, be poured into water, it is in- 
stantly dissolved and converted into hypochlorous acid. The 
reaction is expressed in the following equation : 

cl}o + l}o = ^,[0 + ci}o 

Hypochlorous oxide. Water. Hypoclilorous acid. Hypochlorous acid. 

Both the hypochlorous oxide and the water are converted 
into hypochlorous acid by the exchange of an atom of hydro- 
gen for an atom of chlorine, so that the hypochlorous acid 
may be said to represent water in which 1 atom of chlorine is 
substituted for an atom of hydrogen. 

Thus, by their atomic constitution both potassium hydrate 
and hypochlorous acid are closely related to water. But on 
comparing them together they are found to differ widely in 
their properties, both from each other and from water itself. 
How could it be otherwise with bodies containing elements as 
unlike as potassium and chlorine ? Indeed, the distance which 
separates potassium hydrate and hypochlorous acid is not 
greater than that which separates potassium and chlorine. 
Thus, a difference of elements may imply a marked difference of 
properties between bodies which otherwise present a similar con- 
stitution, and which may be said to belong to the same iype. 

Water is one of these types. Its constitution serves as a 
sort of model for that of a multitude of compounds. It will be 
sufficient to reconsider the examples already cited, and we may 
say that water, potassium hydrate, potassium oxide, hypochlo- 
rous acid, and hypochlorous oxide belong to the water type. 



^^ ^ S 1 S I ^AO 



l}o 



CI f ^ H f ^ H f ^ H 

Hypochlorous Hypochlorous Water. Potassium Potassium 

oxide, acid. hydrate, oxide. 



WATER. to 

The preceding considerations give but a limited idea, but 
one sufficient for the present, of the role played by water in 
cliemical phenomena. This role is one of great importance, 
for water takes part in an immense number of reactions, either 
by its decomposition, its formation, or its combination. 

Water presents still another mode of action. It dissolves 
very many bodies, and this solvent action is exerted upon 
gases, liquids, and solids. 

Solvent Properties of Water. — When a gas dissolves in 
water, it changes its state, it becomes itself liquid, and in lique- 
fying it evolves heat. In the same manner a solid body be- 
comes liquid by the act of solution, but in order to become 
liquid it must absorb heat. Consequently, the solution of a 
gas in water takes place with a production of heat ; that of a 
solid body takes place with a lowering of temperature, or, to 
use a common expression, a production of cold. 

But sometimes this physical phenomenon of the solution of 
a solid body in water, that is, its liquefaction and dijBfusion in 
the liquid, is complicated by a chemical action. 

Experitnent. — If water be poured upon fused and powdered 
calcium chloride, the salt is instantly dissolved with a produc- 
tion of heat. This heat is the evidence of a chemical com- 
bination, and the water has indeed combined with the calcium 
chloride ; if now the solution be sufficiently evaporated, it will 
deposit fine transparent crystals of hydrated calcium chloride. 
The water contained in these crystals, and which is necessary 
for their formation, is what is called icater of crystallization. 
It is contained in definite proportions, and is retained in the 
crystals by affinity. For this reason the combination of water 
with calcium chloride is accompanied by a production of heat. 

If these crystals of calcium chloride be dissolved in water, 
they disappear, and the temperature of the liquid is depressed. 
The physical phenomenon of the solution of a solid body in 
water can thus be separated from the chemical phenomenon 
of its combination with that liquid. 

Natural State of Water. — Water is not met with in a pure 
state in nature. Whether it has rested upon or has flowed over 
the surface of the soil, whether it has fallen in the form of rain, 
mist, or dew, or whether it has just issued from its subterranean 
passages, it always contains various matters in solution. 

It takes up the gases from the atmosphere, and also certain 
bodies which it there finds suspended or in vapor. On the 



80 ELEMENTS OF MODERN CHEMISTRY. 

surface or in the bosom of the earth it dissolves the soluble 
substances which it encounters. Hence the composition of 
natural water presents great variations, according to the origin 
of the water and the localities where it has collected, or the 
soils through which it has travelled. In general, meteoric 
waters^ that is, those which result from the condensation of 
the aqueous vapor diffused through the atmosphere, are more 
pure than those which have collected upon the earth's surface. 
The latter present in their physical and chemical properties, in 
their composition, and in their action upon the animal econ- 
omy, such diiferences that they are classified in several groups. 

Soft or potable waters are distinguished from hard waters. 
The first are such as hold only small quantities of foreign mat- 
ters in solution, and are essentially fit for domestic use. The 
second are too highly charged with saline matters, and princi- 
pally the salts of calcium, to be fit for such purposes. Good 
potable water should be cool, limpid, without odor, should have 
a faint but agreeable taste, which should be neither insipid, 
saline, nor sweet, and should cook and soften vegetables and 
dissolve soap. The purest water is not necessarily the best. 
Thus distilled water, rain-water, and that coming from the 
melting of ice and snow, although more pure, are less salubrious 
than good spring or river water. 

Good potable water should be aerated, that is, it should hold 
in solution the gases contained in the atmosphere : oxygen, 
nitrogen, and carbonic acid. Rain-water takes from the atmos- 
phere a proportion of oxygen, and especially of carbonic acid 
gas, much greater than that in which these gases are contained 
in the air. This must be so, for Dalton has shown that the 
solvent action of water upon a gaseous mixture is measured for 
each gas by the product of its coefficient of solubility and the 
figure expressing the proportion of that gas in the mixture. 
These gases are driven out of water by boiling. 

The following figures give the proportions of the atmospheric 
gases expelled by boiling from a litre of water from the Seine, 
in the month of January, and also the proportions contained in 
a litre of rain-water (Peligot) : 

Water of the Seine. Rain-Water. 



Carbonic acid gas . . 22.6 cubic centimetres. 0.5 c. c. 1.77 

Nitrogen 21.4 15.1 64.47 

Oxygen IM J_A 38.76 

54.1 23.0 100.00 



WATER. 81 

It is seen that the running water contains a larger amount 
of all of the gases than rain-water, and a notably larger pro- 
portion of carbonic acid. 

Solid Hatters dissolved in Wate7\ — Soft waters generally 
contain a small proportion of fixed matters, among which are 
certain salts of calcium and magnesium, certain alkaline salts, 
silica, and organic matters. 

The calcium salts are the carbonate and sulphate, and some- 
times traces of the chloride, nitrate, and phosphate. 

Calciuin carbonate^ or carbonate of lime, is almost insoluble 
in pure water, but dissolves readily in water charged with 
carbonic acid gas ; in such solutions it exists as dicarbonate. 
When water thus charged with calcium dicarbonate is boiled, 
that salt is decomposed, carbonic acid gas is disengaged, and 
neutral calcium carbonate is precipitated. When the propor- 
tion of calcium dicarbonate contained in spring-water is large, 
it may happen that as the water loses carbonic acid gas the 
calcium carbonate is deposited at ordinary temperatures. This 
effect is favored by the tumultuous movements to which spring- 
water is subjected either in flowing over an inclined bed or in 
conducting-pipes. The carbonate then forms a crystalline de- 
posit, which incrusts the interior walls of the pipes and, in 
general, whatever objects may be plunged into such waters, 
which for this reason are called incrusting or 'petrifying 
waters. 

The presence of small quantities of calcium dicarbonate in 
drinking-water may be considered as a good condition, from a 
hygienic stand-point, for the system needs calcareous salts for 
the development and nutrition of the bony structures. 

Calcium sulphate^ or sulphate of lime, exists in solution in 
many waters, especially in spring and well waters. When the 
proportion does not exceed fifteen or twenty centigrammes per 
litre, such water may be used without inconvenience for do- 
mestic purposes. Water largely charged with calcium sulphate 
is called selenitous water ; it does not become clouded on ebul- 
lition. Like all other strongly calcareous w^ater, it does not dis- 
solve soap without first forming a flocculent precipitate. Salts 
of barium produce with such water an abundant white precipi- 
tate of barium sulphate, which is insoluble in nitric acid. Such 
water is unfit for economic purposes. 

In general, the proportion of calcareous salts in potable water 
should not exceed five or six decigrammes per litre ; water 



82 ELEMENTS OF MODERN CHEMISTRY. 

containing more than this is difficult to digest, and is called 
hard water. 

Mineral or Medicinal Waters. — These are waters that by 
virtue of their temperature or chemical constituents exercise 
a special action upon the animal economy, and consequently 
have a therapeutic value. 

They are cold or warm. They are called warm when their 
temperature at the moment of emergence is above 12 or 15°. 
Of course their temperatures vary greatly, covering the whole 
thermometric scale from 25 to 100°. There are numerous hot 
springs in California, Colorado, and Virginia. The tempera- 
ture of the Grand Geyser in Iceland is even above 100° in the 
depths of the tube from which it issues. According to their 
chemical constituents, mineral waters are classified in a number 
of characteristic groups, distinguished either by the predomi- 
nance of certain constituents, or by the presence of principles 
particularly active. These groups are as follows : 

Acidulous or gaseous waters, characterized by the presence 
of free carbonic acid. 

Alkaline icaters, characterized by the presence of a greater or 
less proportion of sodium dicarbonate, or of an alkaline silicate. 

Chalybeate loafcrs, holding a salt of iron in solution. 

Saline ivaters, or those containing certain neutral salts. 

Sulphur loafers, characterized by the presence of hydrogen 
sulphide or other soluble sulphide. 

On arriving at the surface of the earth, certain of these 
mineral waters undergo a change in chemical constitution. 
Such are the sulphur waters which absorb oxygen, as Avill be 
noticed presently. Those containing free carbonic acid lose a 
part of their gas, and it often happens that some of the car- 
bonates held in solution by an excess of carbonic acid become 
insoluble, and are deposited after the escape of that excess. 
This is the principal cause of the deposits which form in the 
biisins and conducting-pipes of many mineral waters. These 
deposits vary greatly in composition ; sometimes they are floc- 
culent or pulverulent, and collect in the form of mud ; some- 
times they form hard concretions or scales. Calcium and 
magnesium carbonates, ferric hydrate, alumina, and silica are 
the most ordinary constituents of such deposits. Besides these, 
arsenic, various metallic oxides, and materials which it would 
be difficult to detect in the water itself, are sometimes concen- 
trated, as it were, in these deposits. Thus, arsenic is detected 



WATER. 83 

much more readily in the ochrey deposits around a ferruginous 
spring than in the water of* the spring itself. 

Acidulous or Gaseous Waters. — Free carbonic acid is 
the characteristic and predominant element of these waters ; it 
is dissolved in the depths of the earth under a pressure much 
greater than that of the atmosphere ; hence a certain portion 
of the gas is disengaged as soon as the water emerges from the 
soil, giving rise to a greater or less effervescence. Gaseous 
waters are cold ; their taste is piquant at the moment of emer- 
gence, but often becomes saline or even alkaline after the dis- 
engagement of the greater part of the carbonic acid gas. Nat- 
ural gaseous waters never consist of a solution of carbonic 
acid in pure water ; they always contain a small quantity of 
saline matters, principally traces of sodic, calcic, and magnesic 
carbonates, and even traces of chlorides and sulphates. Such 
is the composition of the celebrated Seltzer water and of Soultz- 
matt water. The water of certain of the Saratoga springs 
approximates in composition to Seltzer water. 

Alkaline Waters. — These waters possess an alkaline re- 
action, either immediately on their emergence or after the loss 
of their free carbonic acid. This reaction may be due to an 
alkaline silicate, but is generally referable to an alkaline car- 
bonate. Sodium acid carbonate, NaHCO'^, commonly called 
bicarbonate of soda, exists in nearly all waters of this class, 
together with an excess of carbonic acid. Vichy water con- 
tains about 5 grammes of this salt per litre. 

Chalybeate Waters. — Nearly all waters contain traces 
of iron in solution ; chalybeate waters are such as contain 
sufficient of that metal to give them an astringent taste and 
special therapeutic properties. The iron may exist in three 
conditions : 

1. As ferrous carbonate held in solution by carbonic acid. 

2. As ferrous crenate. Berzelius gave the names crenic 
and apocrenic acids to two bodies which are related to peculiar 
acids existing in the soil or humus, and which are known as 
ulmic, humic, and geic acids. Ferrous crenate is soluble in 
water ; its constitution is not known. 

3. As ferrous sulphate. 

Consequently, chalybeate waters may be carbonated, cre- 
nated, and sulphated. 

The ferrous salts are never contained in these waters in large 
proportions. Many ferruginous waters of undoubted efficacy 



84 ELEMENTS OF MODERN CHEMISTRY. 

do not contain more than 4 or 5 centigrammes per litre. 
Wlien exposed to the air they lose the greater part of their 
carbonic acid, and ferrous carbonate is deposited, but this loses 
its carbonic acid and is converted into brown ferric hydrate. 
Such is the manner of formation and the nature of the ochrey 
deposits always noticeable around ferruginous springs. 

Chalybeate waters are widely diffused. Those of Spa and 
Pyrmont, Belgium (carbonated), Bussang in the Yosges, and 
Forges (crenated), and Passy, at Paris, are well known. Cele- 
brated springs of this class exist at Bedford, Pennsylvania ; 
others are widely diffused throughout the United States. 

Saline Waters. — This class includes a great number of 
waters charged with various neutral salts, among which are the 
chlorides, bromides, and iodides. The salts of sodium, mag- 
nesium, and calcium are those more usually met with in these 
waters. According to the predominating or peculiarly active 
principle present, they are classified as chlorinated, sulphated, 
and bromo-iodated waters. The Saratoga springs yield an 
acidulo-saline water. 

Chlorinated Saline Waters. — The chlorides generally found 
in mineral waters are those of sodium, magnesium, and cal- 
cium ; the former is much the more abundant, and constitutes 
one of the most common constituents of mineral waters. It 
communicates to them a pure salty taste, free from bitterness. 
A great number of saline springs serve for the extraction of 
sodium chloride. After the evaporation of the water and the 
deposition of the salt, a mother-liquor remains in which various 
less abundant salts are concentrated, principally the alkaline 
bromides and iodides. 

Sea-water is a chlorinated water. It is well known that it 
contains a notable proportion of sodium chloride (2.5 to 2.7 
per cent.). The common salt is accompanied by the chlorides 
of magnesium and potassium, and by a considemble quantity 
of magnesium sulphate (0.6 to 0.7 per cent.). 

The Dead Sea and the Great Salt Lake of Ut^h are the 
most concentrated saline sources known. The water of the 
latter contains 20 per cent, of sodium chloride. 

Sulphated Saline Waters. — These are characterized by so- 
dium, magnesium, or calcium sulphate. The springs of Carls- 
bad, in Bohemia, contain a large proportion of sodium sulphate, 
together with sodium bicarbonate and sodium chloride. 

The purgative waters of Epsom, England, contain magne- 



HYDROGEN DIOXIDE. 85 

sium sulphate. The waters of Sedlitz, Saidschiitz, and Pullna, 
in Bohemia, contain magnesium sulphate and sodium sulphate. 
Their taste is bitter. The Avon Spring, New York, is of this 
class. 

Bromo-iodafed Waters. — Many mineral waters contain small 
quantities of bromides and iodides, independently of the chlo- 
rides which generally exist in much larger proportions. The 
water of the Dead Sea, so rich in magnesium and sodium 
chlorides, contain 0.43 per cent, of magnesium bromide. The 
Iodine Spring at Saratoga contains a notable proportion of 
alkaline iodides. 

Sulphur Waters. — By this name are designated those 
waters containing a soluble sulphide or sulphuretted hydro- 
gen. They are either natural sulphur waters or accidental 
sulphur loaters. The first contain sodium sulphide ; they are 
generally warm, and contain but little solid matter. They all 
disengage nitrogen on their emergence from the soil. They 
contain a nitrogenized organic matter (baregine), and some- 
times deposit a gelatinous precipitate (glairine). 

Celebrated springs exist in the Pyrenees and at Bagneres- 
de-Luchon. The sulphur springs of Sharon and Avon, in New 
York, and the Red and White Sulphur Springs of Virginia 
are well known. 

Accidental sulphur ivaters are those which are formed upon 
the spot by the reduction of sulphates, and particularly calcium 
sulphate, contained in the waters. This reduction is accom- 
plished by the action of organic matters which impregnate the 
soil, and of which the combustible elements, carbon and hydro- 
gen, remove the oxygen of the sulphates. It is thus that the 
sulphur water of Enghien is formed at the gates of Paris. 

HYDBOaEN DIOXIDE. 

H202 

This remarkable compound was discovered by Thenard in 
1818. It is formed by the action of barium dioxide upon di- 
lute hydrochloric acid. Barium dioxide, powdered and made 
into a fine paste with water, is introduced by small portions 
into cold and dilute hydrochloric acid. It dissolves without 
disengagement of gas, yielding barium chloride and hydrogen 
dioxide. 

BaO^ + 2HC1 = BaCP + H^O' 

Barium dioxide. Hydrochloric acid. Barium clilorido. Hydrogen dioxide. 

8 



86 ELEMENTS OF MODERN CHEMISTRY. 

The barium chloride is converted into sulphate, which pre- 
cipitates, by the cautious addition of dilute sulphuric acid, and 
at the same time hydrochloric acid is regenerated, so that an 
additional quantity of barium dioxide may be added, and the 
operation is several times repeated. 

BaCP + H^SO* = BaSO* + 2HC1 

Sulphuric acid. Barium sulphate. 

The barium chloride finally remaining in solution is exactly 
precipitated by a solution of silver sulphate, and the hydrogen 
dioxide poured off and evaporated in vacuo. 

Pure hydrogen dioxide is a syrupy, colorless, odorless liquid, 
having a density of 1.452. It is very unstable, and readily 
gives up half of its oxygen, being converted into water. This 
decomposition takes place with a brisk effervescence when the 
dioxide is heated towards 100° ; it is also produced by con- 
tact with a great number of bodies, some of which are them- 
selves unaltered, some oxidized, and others even reduced. 
Hence hydrogen dioxide enters into three classes of reactions. 

1. If hydrogen dioxide, or more simply, water charged with 
hydrogen dioxide, be poured into a test-tube containing man- 
ganese dioxide, the hydrogen dioxide is instantly reduced with 
effervescence into water and oxygen. The manganese dioxide 
remains unchanged. Finely divided platinum, gold, silver, and 
carbon act in the same manner. 

2. Hydrogen dioxide energetically oxidizes arsenic and sele- 
nium into arsenic and selenic acids. It converts lead sulphide 
into sulphate. 

PbS + 4W0' = PbSO* -f 4W0 

Lead sulphide. Leail sulphate. 

3. Potassium permanganate, KMnO*, is a salt very rich in 
oxygen ; it dissolves in water, forming a solution having an 
intense purple color. If hydrogen dioxide be added to it, it is 
immediately reduced and decolorized. The oxygen from the 
decomposition of the hydrogen dioxide is in this case added to 
that from the reduction of the permanganate, and both are dis- 
engaged in the free state. 

If hydrogen dioxide be added to a solution of potassium di- 
chromate, the latter assumes a deep blue color, but this rapidly 
disappears, giving place to a green tint. At the same time an 
evolution of oxygen takes place. In this case the reaction is 
complex : a portion of the hydrogen dioxide oxidizes the 



HYDROGEN DIOXIDE. 87 

chromic acid for an instant into blue percliromic acid, but the 
latter is instantly reduced, with disengagement of oxygen, by 
another portion of the hydrogen dioxide, which at the same 
time loses half of its oxygen. 

The oxygen gas liberated comes then at the same time from 
the percliromic acid and the hydrogen dioxide, both of which 
are supersaturated with oxygen, and which mutually reduce 
each other. The perchromic acid formed may be removed 
from the action of the excess of hydrogen dioxide by imme- 
diately agitating the liquid with ether : the latter dissolves the 
acid and assumes a dark-blue color. 

These experiments of reduction are of great interest, and 
permit of but one explanation. The fact of the reciprocal 
reduction of two bodies each supersaturated with oxygen can 
only be explained by admitting that the oxygen of one body 
possesses an affinity for that of the other, and that the oxygen 
which is set free is formed by the union of two atoms, one from 
the hydrogen dioxide, the other from the perchromic or per- 
manganic acid. These two atoms unite to form a molecule of 
oxygen 00. This would represent oxygen in the free state, 
and occupy two volumes. It would be a true combination, and 
we here encounter for the first time the important notion that 
the atoms of certain elements are not isolated when in the free 
state, but combined in pairs, each pair being held together by 
chemical force. Free oxygen would then be oxygen oxide, a 
combination of two atoms of oxygen, both together forming 
a molecule, and occupying two volumes like the molecule of 
water. 

1 molecule of water .... H-O-H = 2 volumes. 
1 molecule of oxygen . . . 0=0 = 2 volumes. 

While the molecular structure of free oxygen or oxygen 
oxide corresponds in a measure to that of hydrogen oxide or 
water, there exists a peroxide of oxygen which corresponds in 
a measure to hydrogen peroxide ; it is ozone. 

Hydrogen dioxide H-O-O-H 

Oxygen dioxide (ozone) Ox' I 

^0 



88 



ELEMENTS OF MODERN CHEMISTRY. 



SULPHUR 

Vapor density compared to air 2.22 

Vapor density compared to hydrogen .... 32. 
Atomic weight S =32. 

Sulphur has been known from the greatest antiquity. In 
certain volcanic countries it is found on the surface of the earth 
in the native state. Sicily and Iceland contain large deposits 
in the neighborhood of extinct volcanoes (solfatares). In order 
to separate it from the earthy matters which accompany it, it 
is subjected in Sicily to distillation in earthen pots (Fig. 32). 




Fig. 32. 

These are arranged in two rows in furnaces, and communicate 
by lateral tubulures with other pots which are placed outside 
of the furnace, and in which the sulphur vapor is condensed. 

Crude sulphur is thus obtained ; it is still mixed with foreign 
matters, from which it is separated by a new distillation. This 
operation, which is called refining, is conducted in an apparatus 
represented in Fig. 33. 

A horizontal cast-iron cylinder. A, receives the melted sul- 
phur from the vessel C, which is heated by the waste gases 
from the furnace, and which serves as a reservoir. The sulphur 
vapor enters a large masonry chamber, B, the floor of which is 



SULPHUR. 



89 



slightly inclined in order tliat tlie condensed liquid sulphur may 
flow towards a tap, H, wliicli can be opened as is necessary. A 
damper, R, that can be regulated by an articulated wire, per- 
mits the closing and opening of the mouth of the cylinder. 
The vault of the chamber is provided with a safety-valve, K, 
which allows of the escape of the expanded air. 

At the commencement of the operation, when the walls of 
the chamber are cold, the sulphur condenses in the form of a 
fine powder, which is known as flowers of sulphur. But when 
the walls of the chamber become heated above the melting- 
point of sulphur, the vapor condenses into a liquid, and on 
opening the tap at H, it is drawn ofl" into a vessel, E, from 
which it is distributed into slightly conical or cylindrical moulds, 
where it solidifies. Roll sulphur is thus obtained. 




Fig. 33. 



Physical Properties. — Sulphur is a lemon-yellow solid. It 
is tasteless, odorless, and brittle ; it is a non-conductor of heat 
and electricity. A stick of sulphur pressed in the hand or 
plunged into warm water produces a crackling sound, and 
finally breaks into pieces ; this is due to the unequal expan- 
sion from the circumference to the centre of the non-conduct- 



90 ELEMENTS OF MODERN CHEMISTRY. 

ing mass of sulphur, the crystaUine particles of which are but 
slightly held together by cohesion. 

The density of sulphur is about 2.03. At 111.5° it melts 
into a brownish-yellow, transparent liquid. If this liquid be 
allowed to cool slowly until a crust forms upon the surface, 
and the crust be pierced and the part still remaining liquid be 
decanted, after removing the crust the interior of the vessel is 
found covered with long, transparent, flexible needles of a 
brownish-yellow color. These crystals are oblique-rhombic 
prisms having a density of 1.98. This is not the only crystal- 
line form assumed by sulphur. If a solution of sulphur in 
carbon disulphide be allowed to evaporate spontaneously, 
right-rhombic octahedral crystals are deposited having a den- 
sity of 2.05. This form is also that of native crystallized 
sulphur. 

Sulphur crystallizes, then, in two distinct forms belonging 
to two distinct crystalline systems. It is dimorphous. It is a 
curious fact that the prisms formed by way of fusion do not 
long retain their transparence and their flexibility. When aban- 
doned for some time to ordinary temperatures, they become 
opaque and brittle. They are then found to be traversed 
by a multitude of planes of cleavage, which are the faces of 
microscopic octahedra similar to those obtained by way of 
solution. 

Reciprocally, the transparent octahedral crystals become 
opaque when maintained for some time at a temperature of 
111° ; they are then transformed into a multitude of little 
crystals of prismatic sulphur. It is seen that the two crystal- 
line modifications of sulphur can be transformed into each 
other. It is a curious instance of dimorphism. 

Sulphur melted in a sealed tube will remain liquid for a 
long time at temperatures below its ordinary point of solidifi- 
cation ; it is then said to be in a state of superfusion. When 
it finally solidifies, it crystallizes in voluminous octahedra 
having the form of crystallized native sulphur (Schlitzen- 
berger). 

There are other and amorphous modifications of sulphur. 

Experiment. — If sulphur be melted in a flask, and the tem- 
perature be gradually raised above its point of fusion, it as- 
sumes a thick consistence and a dark color. At 220° it has a 
brown-red color and is very thick. If while in this state it be 
poured into cold water, it is converted into a soft, transparent, 



SULPHUR. 91 

brownish-yellow, and elastic mass. It has lost all crystalline 
appearance ; it has become amorphous^ and is now soft sulphur. 
When abandoned to itself for several days, it hardens, becomes 
opaque, and reassumes the properties of ordinary sulphur. 
This change takes place immediately if the soft sulphur be 
heated to 90 or 95° ; is then accompanied by a sensible disen- 
gagement of heat (Regnault). 

There are two modifications of soft sulphur. If it be treated 
with carbon disulphide, a part of it is dissolved, and a residue 
remains. The soluble part constitutes soluble soft sulphur ; 
the residue is insoluble soft sulphur (Ch. Sainte-Claire Deville). 
In recently-sublimed flowers of sulphur the sulphur exists in 
the amorphous condition. 

Sulphur boils at 440° ; its vapor is red. At 500° it has a 
density of 6.654 (Dumas). Towards 1000° its density is only 
about one-third as great. According to H. Deville and Troost, 
the vapor density of sulphur, determined at 860° and reduced 
by calculation to 0°, is 2.22. Compared to hydrogen, this 
density is equal to 32, which is the normal density of sulphur 
vapor, and gives its atomic weight. If 1 volume of hydrogen 
weighs 1, 1 volume of sulphur vapor weighs 32 ; the latter 
figure is therefore the atomic weight of sulphur. 

But at a temperature a little above its point of ebullition 
the vapor density of sulphur is Q.Q, or three times greater than 
at 860^ ; this is accounted for by the fact that the sulphur 
does not assume the true gaseous state below a temperature of 
860°. 

Sulphur is insoluble in water, but very slightly soluble in 
alcohol, a little more soluble in ether and benzine. Its best 
solvent is carbon disulphide. 

Chemical Properties. — Sulphur possesses energetic affini- 
ties. It combines directly with a great number of the other 
elements. It is well known that it is combustible, burning 
with a blue flame. Its combustion in air or oxygen produces 
sulphurous oxide. 

Sulphur combines directly with chlorine, bromine, iodine, 
phosphorus, arsenic, and carbon, and with very many of the 
metals. Iron and copper burn in the vapor of sulphur. The 
sulphides thus formed generally possess the atomic constitution 
of the corresponding oxides. Thus, the compound of sulphur 
and carbon, carbon disulphide, is analogous to carbonic acid 
gas. This analogy is maintained between a great number of 



92 



ELEMENTS OF MODERN CHEMISTRY. 



oxygen and sulphur compounds, as will be seen by the follow- 



ing examples : 



H^O water. 

H'^S hydrogen sulphide. 

KOH potassium hydrate. 

KSH potassium sulphydrate. 

C02 carbon dioxide. 

CS2 carbon disulphide. 



•K^O potassium monoxide. 
K^S potassium monosulphide. 
BaO barium monoxide. 
BaS barium monosulphide. 
K^CO^ potassium carbonate. 
K^CS^ potassium sulphocarbonate. 



SULPHYDRIC ACID, OR HYDROaEN SULPHIDE. 

Density compared to air 1.192 

Density compared to hydrogen 17. 

Molecular weight H2S =34. 

This gas, known also as sulphuretted hydrogen, was discov- 
ered by Meyer and Rouelle, and studied by Scheele, in 1777, 
and by Berthollet. 

Preparation. — Hydrogen sulphide may be prepared by 




gently heating antimony trisulphide in a flask with hydrochlo- 
ric acid (Fig. 34). The gas is first passed through a wash- 



HYDROGEN SULPHIDE. 



93 



bottle, B, containing a little water, and may then be collected 
over the pneumatic trough. 

The reaction which takes place is expressed by the following 
equation : 

Sb^S^ + 6HC1 = 2SbCP + 3H^S 

Antimony trisulphide. Hydrochloric acid. Antimony trichloride. 

The gas is generally prepared in the laboratory by the 
reaction of dilute sulphuric acid with ferrous sulphide. The 
operation requires no heat, and the reaction is as follows : 

FeS + H'^SO* = FeSO* + H^S 

Ferrous sulphide. Sulphuric acid. Ferrous sulphate. 

As hydrogen sulphide is largely used in the laboratory, the 
apparatus represented in Fig. 35 is convenient for its ready 
production. It is composed of two large bottles, of which the 




lower apertures are connected by a large caoutchouc tube. In 
one of these bottles is placed a layer of broken glass or coke, 
which is not attacked by sulphuric acid ; upon this is placed 
the ferrous sulphide in fragments. The neck of this bottle is 
closed by a cork, through which passes a glass tube bearing a 
stop-cock. The second bottle is nearly filled with dilute sul- 
phuric acid. The stop-cock of the first bottle being opened, 
the sulphuric acid enters until it attains the same level in both 
bottles, and as soon as it reaches the ferrous sulphide the reac- 
tion commences and hydrogen sulphide is disengaged. If the 



94 ELEMENTS OF MODERN CHEMISTRY. 

stop-cock be closed, the continued evolution of gas drives the 
liquid back into the second bottle, until the disengagement of 
gas ceases, which takes place as soon as the sulphuric acid no 
longer touches the ferrous sulphide. The first bottle then 
serves as a reservoir of hydrogen sulphide, containing the gas 
under a pressure greater than that of the atmosphere, and 
which can be increased by elevating the second bottle. In 
order to obtain a current of the gas, it is sufficient to open the 
stop-cock, and the flow can be regulated at will. 

Physical Properties. — Hydrogen sulphide is a colorless gas. 
It has a penetrating odor of putrid eggs. Under a pressure of 
17 atmospheres, it condenses to a transparent, strongly refract- 
ing liquid, having a density of about 0.91. At — 85.5° this 
liquid solidifies to a white crystalline mass (Faraday). Hydro- 
gen sulphide is soluble in water. At 0°, one volume of water 
dissolves 4.37 volumes; at 10°, 3.58 volumes; and at 20°, 
2.90 volumes. 

Composition. — 2 volumes of hydrogen sulphide contain 2 
volumes of hydrogen and 1 volume of sulphur vapor. 

If a given volume of this gas be introduced into a bent tube 
over mercury (Fig. 22), and a morsel of tin be then introduced 
and heated for about twenty minutes, the hydrogen sulphide is 
decomposed ; the sulphur combines with the tin, and the hy- 
drogen is set free. After cooling, the latter gas occupies a 
volume exactly equal to that of the hydrogen sulphide at first 
contained. 

If, then, from the vapor density of hydrogen sulphide = 17 
we subtract the density of hydrogen = 1 

we find the number 16 

which represents half the density of sulphur vapor. 

It is hence concluded that one volume of hydrogen sulphide 
contains half a volume of sulphur vapor to one volume of hy- 
drogen. 

It is also seen that hydrogen sulphide has exactly the same 
chemical constitution as vapor of water. 

H'^0 =■ 2 volumes or one molecule of vapor of water. 

H'^S = 2 volumes or one molecule of hydrogen sulphide. 

The analogy between sulphur and oxygen is here manifested 
in a striking manner. One atom of each of these elements 
requires two atoms of hydrogen. This is expressed by saying 
that both oxygen and sulphur are diatomic elements. 



HYDROGEN SULPHIDE. 95 

Chemical Properties. — Hydrogen sulphide is combustible, 
burning with a bluish flame. The products of its complete 
combustion are water and sulphurous oxide. When mixed 
with one and a half times its volume of oxygen, it explodes on 
the application of a flame or the passage of an electric spark. 

H^S + 0' = SO' + H'O 

Two volumes. Three volumes. Two volumes. Two volumes. 

When the supply of oxygen is insufficient, the combustion 
is incomplete and sulphur is deposited. 

In the presence of water, this oxidation takes place at ordi- 
nary temperatures, occasioning a deposit of sulphur. In the 
presence of moisture and porous matters it goes further, sul- 
phuric acid being formed. 

Hydrogen sulphide has a feeble acid reaction ; it changes 
blue litmus to a wine-red color. When it reacts with potassium 
hydrate, water and potassium sulphydrate are formed. 

H[S + i}0 ^ ijs + H(, 

Hj'drogen sulphide. Potassium hydrate. Pota'ssium sulphydrate. 

Chlorine, bromine, and iodine decompose hydrogen sulphide, 
combining with its hydrogen. When these bodies are dry, the 
action is energetic, and the sulphur combines with the excess 
of the element employed. If water be present, the sulphur 
is set at liberty. 

Bodies rich in oxygen readily decompose hydrogen sulphide. 

Experimemts. — 1. If a few drops of the strongest nitric acid 
be poured into a jar filled with hydrogen sulphide, the gas is 
instantly inflamed. The nitric acid gives up oxygen, water is 
formed, sulphur is set free, and abundant red fumes appear at 
the same time. 

2. If four volumes of hydrogen sulphide be mixed with two 
volumes of sulphurous oxide over the mercury-trough, a deposit 
of sulphur is at once formed. 

2H^S + SO^ == 2W0 + 3S 

Hydrogen sulphide. Sulphurous oxide. Water. Sulphur. 

(4 volumes.) (2 volumes.) 

Hydrogen sulphide decomposes a great number of metallic 
solutions, forming insoluble sulphides, which are precipitated. 

Experiments. — 1. If a solution of hydrogen sulphide be 
added to a solution of blue vitriol or cupric sulphate, a brown 



96 ELEMENTS OF MODERN CHEMISTRY. 

precipitate of cupric sulphide is formed. The reaction is 
expressed bj the following equation : 

CuSO* -f H^S = CuS + H'^SO* 

Cupric sulphate. Cupric sulphide. Sulphuric acid. 

2. By an analogous reaction, a solution of plumbic acetate, 
or a paper impregnated with that salt, is at once blackened by 
the presence of hydrogen sulphide. 

Hydrogen sulphide acts as a poison if inhaled in large 
quantities or for any length of time. 

HYDROGEN PERSULPHIDE. 

This compound, discovered by Thenard, is analogous to hy- 
drogen dioxide. It is prepared by pouring, drop by drop, a 
solution of calcium disulphide into dilute hydrochloric acid. 

CaS^ + 2HC1 r= CaCP + H^S^ 

Calcium disulphide. Hydrochloric acid. Calcium chloride. Hydrogen disulphide. 

Hydrogen disulphide is formed and collects at the bottom 
of the vessel in the form of a yellowish oil, having a disa- 
greeable, irritating odor. Towards 60 or 70° it decomposes 
rapidly into hydrogen sulphide and sulphur. 

H^S'^ = H'^S + S 

This decomposition takes place slowly at ordinary tempera- 
tures. 

Hofmann attributes to this body the formula H^Sl He has 
obtained a compound of this sulphide with an alkaloid, strych- 
nine, the analysis of which has led him to conclude that there 
are three atoms of sulphur in a molecule of the persulphide of 
hydrogen. 

. OXYGEN ACIDS OF SULPHUR. 

1 . Sulphur forms three compounds with oxygen : 

a A 1 -1 ark2 f sulphurous anhydride or 

toulphurous oxide feU < i r, j- -j 

^ [ sulphur dioxide. 

ri 1 1 • . I cirv3 ( sulphuric anhydride or 

bulphuric oxide feO'^ < ^ , , ^ • • i 
^ [ sulphur trioxide. 

-n IT,- • 1 ci2/-k7 i recently discovered by 
Persulphuric oxide b'O^ j E tl ^1 t 



SULPHUROUS OXIDE. 97 

2. By combining with a molecule of water, these oxides are 
converted into the corresponding acids. 

SO^ + H'O = W^O' sulphurous acid. 
SO^ + H'^0 = H^SO* sulphuric acid. 

3. There are two other important acids of sulphur, hypo- 
sulphurous and hyposulphuric acids. The former may be con- 
sidered as sulpho-sulphuric acid, that is, sulphuric acid in 
which 1 atom of oxygen is replaced by an atom of sulphur. 

H'SO* sulphuric acid. 

H\SO^)S sulpho-sulphuric or hyposulphurous acid. 
Hyposulphuric acid may be considered as resulting from the 
addition of sulphurous oxide to sulphuric acid. 

SO^ + H'SO* =•- H'^S^O^ hyposulphuric acid. 

4. These are not the only known sulphur acids. 
Hyposulphuric acid, which is called also dithionic acid, is 

the first of a series of acids, each of which contains 2 atoms of 
hydrogen and 6 atoms of oxygen, the number of sulphur atoms 
regularly increasing. This series is called the tliionic series. 
The following is the nomenclature and composition of the 
acids : 

H'^S'^0® dithionic, hyposulphuric acid. 

W^'O^ trithionic acid. 

H^S^O^ tetrathionic acid. 

H'^S^O^ pentathionic acid. 

5. Schiitzenberger has recently made known a new sulphur 
acid, which he has named hydrosulphurous acid, and which is 
formed by the action of zinc upon sulphurous acid, as will be 
described farther on. The composition of this acid is repre- 
sented by the formula 

H^SO^ 

There is an interesting relation between this acid and sul- 
phurous and sulphuric acids. 

H^SO^ hydrosulphurous acid. 

H'^SO' sulphurous acid (not yet isolated). 

H^SO* sulphuric acid. 

SULPHUROUS OXIDE. 

Density compared to nir ........ 2.234 

Density compared to hydrogen 32. 

Molecular weight SO^ =64. 

E 9 



98 



ELEMENTS OF MODERN CHEMISTRY. 



Sulphurous oxide or sulphurous acid gas may be prepared 
by decomposing sulphuric acid with copper. The metal in 
small clippings and the acid are introduced into a flask fitted 




Fig. 36. 



with a delivery-tube (Fig. 36) ; heat is applied and the gas 
collected over the mercury-trough. The reaction which takes 
place is expressed by the following equation : 



Cu 

Copper. 



2H2SO* = CuSO* + 

Sulphuric acid. Cnpric sulphate. 



2E'0 + SO^ 



A solution of sulphurous acid in water is often needed in 
the laboratory. It may be conveniently prepared by reducing 
sulphuric acid by charcoal ; the products of the reaction are 
water, and sulphurous and carbonic acid gases. 



2H20 + 2S0' 



Carbon dioxitlo. 



2H2SO* + C 

Sulphuric acid. 

The mixed gas is passed through a series of bottles contain- 
ing water, which dissolves the sulphurous oxide, but takes up 
only an insignificant quantity of the carbon dioxide. 

Physical Properties. — Sulphur dioxide is a colorless gas 
having a pungent, suffocating odor. It is readily liquefied by 
being led into a vessel surrounded by a mixture of ice and salt. 
It condenses at ordinary temperatures, under a pressure of 
about two atmospheres. The liquid has a density of 1.45 ; it 
boils at — 10°, and produces great cold by its evaporation ; on 
this account it is used for the manufacture of ice, and in other 
cases where intense cold is required. — 73° may be obtained 



SULPHUROUS OXIDE. 99 

by the evaporation of liquid sulphurous acid aided by double- 
acting pumps (Raoul Pictet). 

Water at 0° dissolves 79.9 times its volume of sulphurous 
oxide, and only 39.4 volumes at 20°. 

Experiments. — 1. If a small quantity of mercury contained 
in a porcelain capsule be covered with a deep layer of liquid 
sulphurous oxide, and the evaporation of the latter be favored 
by directing a rapid current of air over its surface, the mercury 
is frozen into a solid button. 

2. When liquid sulphurous acid is poured into not too great 
a quantity of water, a part of it is dissolved, but the excess 
absorbs heat from the mass of liquid, volatilizes suddenly, and 
the water is frozen. 

Chemical Properties. — Sulphurous oxide is not decom- 
posed by heat. It is incombustible, and extinguishes burning 
bodies. 

Its most striking property is its affinity for oxygen. If a 
mixture of two volumes of sulphurous oxide and one volume 
of oxygen be passed through a tube containing slightly heated 
spongy platinum, the two gases combine, forming sulphuric 
oxide (Kuhlmann). 

A solution of sulphurous oxide in water slowly absorbs oxy- 
gen, and is converted into sulphuric acid. It may be admitted 
that the aqueous solution contains the veritable sulphurous acid. 

Sulphurous acid. Sulphuric acid. 

Sulphurous acid reduces a great number of oxidized bodies. 
At ordinary temperatures it takes the oxygen from iodic acid, 
setting free the iodine ; but the latter disappears on the addi- 
tion of an excess of sulphurous acid, sulphuric and hydriodic 
acids being formed. 

H^SO' -I- WO + r = H^SO* + 2HI 

It decolorizes the purple solution of potassium permanganate, 
forming manganese sulphate and potassium sulphate. It con- 
verts arsenic acid into arsenious acid. It combines directly 
with lead dioxide, forming lead sulphate. 

PbO^ + SO^ = PbSO* 

Lead dioxide. Lead sulphate. 

Chlorine will unite directly with sulphurous oxide. If a 
mixture of equal volumes of chlorine and sulphurous oxide be 



100 ELEMENTS OF MODERN CHEMISTRY. 

exposed to sunlight, the two gases combine, forming a liquid 
having a suffocating odor. It is sidphuryl chloride. Its den- 
sity is 1.66, and its boiling-point is 77°. It may be regarded 
as sulphur trioxide in which one atom of oxygen is replaced 
by two atoms of chlorine. 

SO^ = (S0^)"0 sulphuryl oxide or sulphuric oxide. 
SO'CP = (SO"'j"CP sulphuryl chloride. 

In these reactions in which the sulphurous oxide combines 
directly with either one atom of oxygen or two atoms of chlorine, 
it plays the part of an element ; it is a compound radical^ and 
this radical is diatomic^ because it unites with two atoms of the 
monatomic element chlorine, or with one atom of the diatomic 
element oxygen, which is equivalent to two atoms of chlorine. 

In the formulae given, the diatomicity is expressed by the 
accents ". 

Sulphurous acid bleaches various vegetable and animal mat- 
ters. A bouquet of violets or a rose is bleached in a few minutes 
by a solution of sulphurous oxide. 

Sulphurous oxide is employed in the arts to bleach wool. 

HYDKO-SULPHUROUS ACID. 

H2S02 

"While sulphurous acid reduces a number of bodies, it is in 
its turn reduced by the action of zinc upon its aqueous solution. 
A yellow liquid is thus obtained which energetically bleaches 
indigo and litmus solutions (Schonbein). Schiitzenberger has 
shown that the liquid gifted with these properties contains the 
zinc salt of a new acid, which he has named liydrosidphurous. 
This acid is formed by the combination of hydrogen with sul- 
phurous oxide. The reaction is expressed by the following 
equations : 



ffSO-^ + Zn = 

Sulphurous acid. Zinc. 


Zinc sulphite. 


SO^ -f H^ 

Sulphurous oxide. 


Hydrosulphurous acid. 



When this liquid is treated with very dilute sulphuric acid, 
it gives a liquor of a dark orange-yellow color, having ener- 
getic bleaching powers. It then contains hydrosulphurous 
acid. It soon becomes clouded and deposits sulphur. This 



101 

acid is not stable, but its acid sodium salt is more so ; the latter 
has the composition NaHSO^ It readily absorbs oxygen from 
the air, being converted into sodium acid sulphite. 

NaHSO' -f = NaHSO^ 

This oxidation is also brought about by the presence of cer- 
tain metallic salts, such as those of copper, mercury, and lead. 
In this case the metal is reduced and precipitated, and the 
hydrosulphite is decomposed, yielding sulphurous oxide. 

NaHSO' + CuSO* = NaHSO* -f SO' + Cu 

Sodium hydrosulphite. Cupric sulphate. Sodium acid sulphate. 

Sodium acid hydrosulphite may be obtained by the electro- 
lysis of a solution of sodium acid sulphite. In this case the 
hydrogen, which would otherwise be disengaged at the negative 
pole, accomplishes the reduction. 

NaHSO^ + ff = NaHSO' -f H'O 



SULPHUR TRIOXIDE, OR SULPHURIC OXIDE. 

(sulphuric anhydride.) 

Vapor density compared to hydrogen 40. 

Molecular weight SO^ =^80. 

Sulphur trioxide is formed by the union of oxygen with sul- 
phurous oxide in the presence of finely-divided platinum. 

It is prepared by gently heating fuming sulphuric acid in a 
retort ; vapors are given oiF which, when condensed in a re- 
ceiver surrounded by a freezing mixture, solidify into a white 
mass, having a fibrous appearance and a silky lustre. 

Sulphur trioxide boils at a temperature between 30 and 35°. 
At ordinary temperatures it produces white fumes in the air 
by condensing the atmospheric moisture. Its most striking 
property is its affinity for water ; when thrown into that liquid, 
it becomes hydrated with such energ^y that a portion of the 
water is suddenly vaporized, and a hissing noise is produced 
similar to that heard on plunging a red-hot iron into water. 

Sulphuric acid is formed by the reaction. 

SO^ + H^O = H'SO* 
9* 



102 ELEMENTS OP MODERN CHEMISTRY. 

SULPHURIC ACID. 

Molecular weight IPSO* =98. 

This acid, which has been known for centuries, was formerly 
obtained by the distillation of ferrous salphate. Large quan- 
tities of it are now consumed in the arts, and it is manufac- 
tured in extensive apparatus known as leaden chamhers. Sul- 
phurous oxide is conducted into these chambers, where it 
meets with nitric acid, by which it is oxidized. 

SO'^ + 2HN0^ = H^SO* -f 2N0^ 

Nitric acid. Nitrogen peroxide. 

The products of the first reaction are sulphuric acid and 
nitrogen peroxide (red vapors) ; but the latter is decomposed 
by steam, which is injected into the chamber ; nitric acid is 
regenerated and nitrogen dioxide is formed. 

3N0^ + H^O = 2HN0^ + NO 

Nitrogen peroxide. Nitrogen dioxide. 

But the nitrogen dioxide is not lost ; it combines with the 
oxygen of the air contained in the chamber, and is reconverted 
into nitrogen peroxide. 

NO + = NO^ 

The latter is again decomposed into nitric acid and nitrogen 
dioxide by the action of water, and the sulphurous oxide which 
continually arrives in the chamber always encounters nitric 
acid, by which it is converted into sulphuric acid. It is a 
continuous operation, which theoretically leaves no residue, 
and permits of the conversion of an indefinite amount of sul- 
phurous oxide into sulphuric acid. 

It is really the oxygen of the air, continually absorbed and 
given up by the nitrogen dioxide, which effects the oxidation 
of the sulphurous oxide ; the nitric acid is the direct agent, 
and the nitrogen dioxide is intermediate, for it is the vehicle 
for the transfer of the oxygen. 

Fig. 3*7 represents a section of a series of leaden chambers 
for the manufacture of sulphuric acid. 

Sulphur is burned in two furnaces, AA, and the heat gen- 
erated is employed to boil the water contained in the boilers 



SULPHURIC ACID. 



103 




104 ELEMENTS OF MODERN CHEMISTRY. 

above the flame, the steam being distributed to the chambers 
by the pipes c d. The sulphurous oxide, together with a 
great excess of air, passes through the pipes BB into a leaden 
drum, C. A thin layer of sulphuric acid charged with nitrous 
products trickles over the inclined shelves in the drum. The 
gases pass first into the chamber C, then into D, where they 
meet with nitric acid, which falls in thin layers over a double 
cascade, EE, in such a manner as to present a large surface for 
the action of the sulphurous oxide. The sulphuric acid which 
is formed in this chamber is charged with nitrous products ; it 
is therefore allowed to flow by the inclined tube F into the 
chamber C, where it encounters an excess of sulphurous oxide, 
and which is called the denitrifier. The sulphurous oxide, the 
excess of air, and the nitrogen peroxide pass from D into the 
large chamber HH, into which steam is projected by several 
jets. Here the larger portion of the sulphuric acid is pro- 
duced, and the reaction is completed in another chamber. In 
the engraving the last two chambers are not fully represented. 
The gases from the last chamber enter a refrigerator, in which 
the condensation takes place ; they are lastly conducted into a 
leaden column, R, filled with coke which is kept saturated 
with sulphuric acid by a thin stream from the reservoir 0. 
This acid completely absorbs the nitrogen dioxide, and descends 
by the tube ha into the reservoir i, situated near the furnace. 
As soon as this reservoir is full, the stop-cock r is closed, and 
/ is opened ; the pressure of the steam then forces the acid 
up into the reservoir g, which feeds the first drum. The gas 
which escapes from the last column, which is known as Gay- 
Lussac's column, consists of nitrogen charged with an insig- 
nificant quantity of nitrous products. 

The acid which is drawn from the chambers is not suffi- 
ciently concentrated, having a density of only about 1,5. It 
is first evaporated in leaden vessels until it becomes strong 
enough to act upon the lead, and the concentration is then fin- 
ished in large platinum retorts. The excess of. water is thus 
driven out. The concentrated acid possesses a density of 
1.842. 

In many manufactories pyrites is burned instead of sulphur. 
Sulphurous oxide is produced, and a residue of ferric oxide 
remains. 

Purification of SitlpJmric Acid. — The sulphuric acid of 
commerce contains impurities. It holds in solution a small 



SULPHURIC ACID. 105 

quantity of lead sulphate, formed in the evaporating basins ; it 
is often charged with nitrous products, and sometimes with ar- 
senic acid, when the sulphurous oxide employed in its prepa- 
ration has been obtained by the combustion of arsenical pyrites. 
It may be freed from these impurities by distillation. The 
nitrous products are first disengaged, and are found in the first 
portions of the distillate, which must be rejected. Pure sul- 
phuric acid then passes ; the lead sulphate and arsenic acid 
remain in the retort with the last portions of the acid, which 
must not be distilled. 

The operation may be conducted in a glass retort connected 
with a cooled receiver. The retort should be heated laterally 
by an annular flame so that explosive evolution of vapor may 
be avoided, and it is well to introduce some platinum wires with 
the acid, and to cover the retort with a sheet-iron hood. 

Constitution of Sulphuric Acid. — Since oxygen combines 
directly with sulphurous oxide to form sulphuric oxide, the 
latter may be regarded as sulphuryl oxide, SO'^0. 

Sulphuric acid is the hydrate of this oxide. 

SO^ -f H^O = H^SO* 

The following experiment indicates the relations which exist 
between the elements composing this hydrate. 

If sulphuryl chloride be poured into water, it disappears, 
sulphuric acid and hydrochloric acid being formed. 

SO^{c! + ioH = S0^{8h + 2HC1 

Snlpliuryl 2 molecules Sulplmric 2 nioleciilos 

chloride. of water. acid. hydrochloric acid. 

Sulphuric acid is thus formed by the decomposition of 2 
molecules of water, of which 2 atoms of hydrogen have been 
removed by 2 atoms of chlorine, and replaced by the group 
SO^. It may then be truly said that sulphuric acid is derived 
from two molecules of water by the substitution of the diatomic 
radical (SO^)" for two monatomic atoms of hydrogen. 

H.OH ^^^^ JOH 

2 molecules of water. Sulphuric acid. 

If the composition of sulphuric acid be compared to that 
of sulphuryl chloride, from which it may be formed, it will be 



106 ELEMENTS OF MODERN CHEMISTRY. 

seen that both compounds contain the same nucleus or radical 
SO'^ and that instead of the two atoms of chlorine of the 
chloride, the acid contains two groups OH. The group OH 
is a residue, as it were, which represents a molecule of water 
minus one atom of hydrogen, and which is called hydroxyl. 
It is a monatomic group, and sulphuric acid is formed by the 
saturation of the affinity of the diatomic radical sulphuryl by 
two monatomic groups hydroxyl, which replace the two atoms 
of chlorine of sulphuryl chloride. Williamson has described 
an intermediate compound in which the radical sulphuryl is 
combined with one atom of chlorine and one OH group. 

SO' { C} SO' { C'jj SO' { og 

Sulphuryl chloride. Sulphuryl chlorohyilrate. Sulphuric acid. 

The sulphur in sulphuric acid is hexatomic. 

O 

HO-S-OH 

II 
O 

Physical Properties. — Sulphuric acid is a colorless oily 
liquid ; its density at 12° is 1.842 (Marignac). Its boiling-point 
is 325°, and it solidifies at — 34°. If it be crystallized several 
times at a low temperature, and the part remaining liquid be 
decanted off each time, the melting-point is gradually raised to 
-f-10.5°, where it remains stationary. According to Marignac, 
the acid which solidifies and fuses at -|-10.5° constitutes the 
true monohydrated acid, H'-^SO^ At a temperature about 40° 
it emits some fumes, and between this point and 290° it disen- 
gages a small quantity of vapor of sulphuric oxide. At 290° 
it begins to boil, but its boiling-point soon rises to 338°, where 
it remains. Such are, according to Marignac, the properties of 
monohydrated sulphuric acid. According to this chemist, the 
acid purified by simple distillation, and boiling at 325°, still 
contains a small amount of water. 

Chemical Properties. — When exposed to a red heat, sul- 
phuric acid decomposes into sulphurous oxide, oxygen and 

H^SO* = SO^ + + H^O 
Many bodies having an affinity for oxygen reduce sulphuric 



SULPHURIC ACID. 107 

acid by the aid of heat. Thus sulphur effects the reduction, 
being at the same time oxidized to sulphurous oxide. 

2H^S0* + S = 3S0' + 2H'^0 

We have already studied the action of charcoal and copper 
upon sulphuric acid when boiled with that liquid, and we have 
seen that zinc and iron decompose the dilute acid with evolu- 
tion of hydrogen and formation of a sulphate. 

Sulphuric acid has a strong affinity for water. When four 
parts of sulphuric acid are quickly mixed with one part of 
water, the temperature rises to above 100°. If the experiment 
be made with large quantities, it is not without danger, and re- 
quires prudence lest part of the acid be projected from the vessel. 

Experiments. — If four parts of sulphuric acid be quickly 
added to one part of snow, the latter is immediately liquefied 
and a notable elevation of temperature takes place ; for the 
energy of the combination of the sulphuric acid with the water 
is so great that the heat produced by the union is greater than 
that consumed in the liquefaction of the ice. 

But if four parts of snow be mixed with one part of sul- 
phuric acid, the result is the reverse ; there is a lowering of 
temperature. 

The affinity of sulphuric acid for water is manifested in a 
number of reactions. In the following it is sufficiently power- 
ful to cause the formation of the water it requires : 

If a morsel of sugar be moistened with sulphuric acid, it 
becomes blackened and carbonized in a few minutes. The sugar 
contains no water already formed, but independently of carbon 
it contains hydrogen and oxygen in the proportions necessary 
to form water, so that the latter compound is produced by the 
influence of the sulphuric acid, and a carbonaceous matter 
remains. 

This water which is absorbed by sulphuric acid with so much 
energy, combines with the acid in a manner analogous to that 
in which water of crystallization combines with certain salts. 
Indeed, if sulphuric acid to which 18.3 per cent, of water has 
been added be exposed to a temperature of 0°, large prismatic 
crystals are formed, which remain solid even at a temperature 
of -j-**^" or -|-8°. The composition of these crystals is ex- 
pressed by the formula H^SO*,H^O. They constitute a dihy- 
drated acid, for they result from the union of two molecules 
of water with one molecule of sulphuric oxide. 



108 ELEMENTS OP MODERN CHEMISTRY. 

Sulphuric acid is a dibasic acid ; that is, it contains two atoms 
of hydrogen that are replaceable by an equivalent quantity of 
metal. This substitution takes place when the acid is treated 
with a hydrate, such as potassium hydrate, or with an oxide, 
such as lead oxide. 

ffSO* -f 2K0H = K^SO* -1- 2H^0 

Potassium hydrate. Potassium sulphate. 

H^SO* + PbO = PbSO* + H^O 

Lead oxide. Lead sulphate. 

When saturated with potassium hydrate, the sulphuric acid 
is converted into potassium sulphate, and, in the salt, two atoms 
of potassium replace the two atoms of hydrogen of the acid. 
In the case of the lead oxide, on the contrary, the reaction, 
which is only a double decomposition, takes place so that a 
single atom of lead replaces the two atoms of hydrogen. The 
metal lead is then said to be diatomic ; that is, one atom of 
lead is capable of replacing two atoms of a monatomic element 
such as hydrogen, and one atom of lead is equivalent to two 
atoms of potassium. 

Sulphuric acid may be detected by the following reactions, 
which are also applicable to the soluble sulphates. 

In solutions containing sulphuric acid or a sulphate, barium 
salts produce a white pulverulent precipitate, which is insolu- 
ble in either cold or hot nitric acid ; this precipitate is barium 
sulphate. When mixed with an excess of charcoal and heated 
to whiteness, it is converted into barium sulphide. 
BaSO* + 4C = 4C0 BaS 

Barium sulphate. Carbon monoxide. Barium sulphide. 

The sulphide of barium disengages hydi'ogen sulphide when 
it is moistened with hydrochloric acid ; this gas may be recog- 
nized by its odor and by its blackening a paper impregnated 
with lead acetate. 

FUMINO SULPHURIC ACID. 

Fuming sulphuric acid, or Nordhausen sulphuric acid, as it 
was formerly called, can be regarded as a combination of sul- 
phuric acid and sulphuric oxide. 

H^SO* -f SO^ = H^S^O' = 

S0^< 
OH 



HYPOSULPHUROUS ACID. 109 

It is a light-brown, oily liquid. At 0° it solidifies into a leafy 
mass. It gives off white fumes in the air. When heated, it 
decomposes into sulphuric oxide and sulphuric acid. It is ob- 
tained in the arts by the distillation of ferrous sulphate that has 
been previously transformed into ferric subsulphate by roasting. 

This subsulphate is calcined in stoneware retorts ; it gives 
off sulphuric oxide when it is perfectly dry, but as it is difficult 
to entirely free it from water of crystallization, the vapor of 
sulphuric oxide is mixed with that of sulphuric acid, and the 
mixed vapors are condensed in cooled receivers. The residue 
of the distillation is ferric oxide, Fe'^Ol 

HYPOSULPHUROUS OR SULPHO-SULPHURIC 
ACID. 

H2S(S03} 
This acid is not known in the free state. When sodium 
hyposulphite is treated with dilute sulphuric acid, the hypo- 
sulphurous acid set free is at once decomposed into sulphurous 
acid and sulphur. 

Na^S^O^ -h H^SO* = Na^SO* + ffSO' + S 

Sodium hyposulphite. Sodium sulphate. 

Sodium hyposulphite is formed when sulphur is boiled with 
a solution of sodium sulphite. 

Na^SO^ -f S = Na^SCSO^) 

Sodium sulphite. Sodium hyposulphite. 

It is a very soluble salt, forming voluminous crystals. 
HYPOSULPHURIC ACID. 

If fuming sulphuric acid represent a combination of sul- 
phuric acid and sulphuric oxide, hyposulphuric acid can be 
regarded as resulting from the union of sulphuric acid with 
sulphurous oxide. 

SO^H^SO* fuming sulphuric acid. 
SOIH'SO* hyposulphuric acid. 

Preparation. — Hyposulphuric acid is prepared by passing 
sulphurous oxide into water in which manganese dioxide is sus- 
pended. 

2S0' + MnO^ = MnS^O^ 

Manganese dioxide. Manganese hyposulphate. 
10 



110 ELEMENTS OF MODERN CHEMISTRY. 

Manganese hyposiilphate is thus formed, and this is con- 
verted into barium hyposulphate by a double decomposition 
with barium sulphide. The liquid is separated from the man- 
ganese sulphide by filtration, and exactly decomposed with 
dilute sulphuric acid. Barium sulphate is precipitated, and the 
hyposulphuric acid remains in solution. The liquid is then 
concentrated in vacuo. 

Properties. — Hyposulphuric acid is a very acid, syrupy 
liquid, having a density of 1.347. It is not stable ; when 
boiled it decomposes into sulphuric acid and sulphurous oxide. 

PERSULPHURIC OXIDE. 

This body has been very recently discovered by Berthelot, 
who obtained it in the pure state by the action of silent elec- 
tric discharges of high tension upon a mixture of equal vol- 
umes of sulphurous oxide and oxygen, both perfectly dry. 
Persulphuric oxide is formed, and there remains a residue of 
oxygen. 

S^O* + 0^ == S^O^ -4- 

4 vol. sulphurous oxide. 4 vol. oxygen. Persulphuric oxide. Oxygen. 

When pure it is solid at ordinary temperatures, crystallizing 
sometimes in grains, sometimes in thin and flexible transparent 
needles. Sometimes it remains liquid. 

It is not stable, and decomposes spontaneously in about two 
weeks. When heated, it decomposes rapidly into sulphuric 
oxide and oxygen. 

S^O^ = 2S0^ -\- 

Persulphuric oxide. Sulphuric oxide. 

Water dissolves it with production of dense fumes and a 
brisk effervescence due to the disengagement of oxygen. The 
liquid then contains sulphuric acid. At the same time a small 
quantity of persulphuric acid, H^S'O^, or HSO*, is formed, 
which soon decomposes into sulphuric acid and oxygen. 

This persulphuric acid, which is very unstable, would be 
analogous to permanganic acid ; its formation is expressed by 
the following equation : 

S^O^ + WO = 2HS0* 



SELENIUM AND TELLURIUM. Ill 

According to Berthelot, persulphuric acid is formed by the 
electrolysis of concentrated solutions of sulphuric acid. It 
would also be formed by the careful addition of a solution 
of hydrogen dioxide to sulphuric acid slightly diluted with 
water. 

2H2SO* + = ffO + 2HS0* 

It is by no means certain that the formula HSO* represents 
the composition of a molecule of persulphuric acid. It is pos- 
sible that this formula must be doubled as indicated above. 
At present this point cannot be decided. 



SELENIUM AND TELLURIUM. 

These two rare elements present a great analogy to sulphur. 

Selenium was discovered by Berzelius in certain Swedish 
pyrites. Like sulphur, selenium has two allotropic forms, one 
crystalline, the other vitreous and amorphous. The crystalline 
variety begins to melt above 217°, but liquefies only at 250° 
(Eegnault) ; after rapid cooling it solidifies into a dark -brown 
mass. Its density is 4.8 when crystallized, and 4.3 when vit- 
reous. When heated in the air to a temperature above its 
melting-point it takes fire and burns with a blue flame, being 
converted into selenious oxide, SeO'^ When sulphurous acid 
is added to a solution of selenious oxide the latter is reduced, 
sulphuric acid is formed, and the selenium is precipitated in 
the form of brown -red flakes. Its compound with hydrogen 
is a colorless gas having a fetid and irritating odor. 

Tellurinin is still more rare than selenium ; it occurs com- 
bined with gold and other metals in certain minerals of Tran- 
sylvania and Hungary, and also in the Rocky Mountain gold 
region in the United States. It has the external appearance 
and the lustre of a metal. Its color is silvery-white ; its den- 
sity 6.25. It melts at about 500°, and can be volatilized at a 
white heat in a current of hydrogen. It has a great tendency 
to crystallize. When heated in the air it burns with a green- 
ish-blue flame, forming tellurious oxide, TeO'^ Its compound 
with hydrogen is a gas having an odor analogous to that of 
hydrogen sulphide. 

The following table shows the analogy between the principal 
compounds of sulphur, selenium, and tellurium : 



112 



ELEMENTS OF MODERN CHEMISTRY. 



H^S 


H^Se 


H^Te 


Ijdrogen sulphide. 


Hydrogen selenide. 


Hydrogen telluride 


SO^ 


SeO^ 


TeO^ 


Sulphurous oxide. 


Selenious oxide. 


Tellurions oxide. 


SO^ 


[SeO^] 


TeO^ 


Sulphuric oxide. 


Selenic oxide. 


Telluric oxide. 


[H^SO^] 


H^SeO^ 


H^TeO^ 


Sulphurous acid. 


Seleuious acid. 


Tellurions acid. 


ffSO* 


H^SeO* 


HTeO^ 


Sulphuric acid. 


Selenic acid. 


Telluric acid. 



CHLORINE. 

Density compared to air 2.44 

Density compared to hydrogen 35.5 

Atomic weight CI = 35.5 

Chlorine was discovered by Scheele in 1774, and was first 
recognized as an element by Gray-Lussac and Thenard in 1809, 
and by Sir Humphry Davy in 1810. 

Preparation. — One part of manganese dioxide in coarse 
powder and six parts of common hydrochloric acid are intro- 






Fig. 38. 



duced into a flask fitted with a safety-tube and delivery-tube 
(Fig. 38). The reaction begins in the cold ; chlorine gas is 



CHLORINE. 



113 



disengaged, and may be collected over salt water. As soon as 
the disengagement of gas diminishes, it may be re-established 
by the application of a gentle heat. 

It is more convenient to collect the gas by dry displacement, 
and it may be obtained pure and dry by being conducted 
through a wash-bottle containing a small quantity of water, and 
a tube containing calcium chloride, as represented in the figure. 
It is then passed, by means of a tube bent at a right angle, 
into a dry jar. The chlorine being heavier than the air, col- 
lects at the bottom of the jar and gradually drives out the air, 
and the uniform greenish color of the whole of the gas in the 
jar indicates when the latter is completely filled. 

If it be desired to prepare a solution of chlorine in water, 
the gas may be passed through a series of Wolff's bottles con- 




taining water, the contents of the first bottle being rejected, 
serving merely to wash the gas (Fig. 39). 

The reaction which takes place in the preparation of chlo- 
rine is a double decomposition between the manganese dioxide 
and the hydrochloric acid. Water and manganese chloride 
are formed, and chlorine is set free. 

MnO^ -f 4HC1 = 2H20 + MnCP + CP 

Manganese dioxide. Hydrochloric acid. Manganese chloride. 

Physical Properties. — Chlorine is a greenish-yellow gas 
10^ 




114 ELEMENTS OF MODERN CHEMISTRY. 

having a strong and suffocating odor. A litre of this gas 
weighs 3.1G gr. It may be liquefied at 15^ by a pressure of 
four atmospheres. A small quantity of the liquid may easily 
be prepared in the following manner : 

Some crystals of chlorine hydrate are introduced into a tube 
of thick glass closed at one end and bent in the middle ; the 

other end is then hermetically 
sealed at the blast-lamp. The 
branch containing the crystals is 
then heated in a water-bath, while 
the other branch is cooled in a 
freezing mixture (Fig. 40). The 
hydrate of chlorine breaks up 
into water and chlorine, and the 
greater part of the latter is disen- 
gaged, and condenses by its own 
pressure into a deep-yellow liquid, 
which collects in the cooler limb 
of the tube (Faraday). 
Chemical Properties. — One volume of water at 8° dissolves 
3 volumes of chlorine ; at 17°, 2.42 volumes. The saturated 
solution has a yellow color. When it is exposed to a tempera- 
ture of 0°, it deposits crystals containing 27.7 per cent, of 
chlorine, and 72.3 per cent, of water, and constituting a hydrate 
of chlorine corresponding to the formula CP -{- lOH^O (Fara- 
day). 

Chlorine possesses powerful affinities. It unites directly 
with the greater number of the other elements, and the com- 
bination frequently takes place with such energy that luminous 
heat is produced. 

Experiments. — If powdered antimony or arsenic be sprinkled 
into a jar containing dry chlorine, each particle of the black 
powder burns with a bright spark as soon as it enters the atmos- 
phere of chlorine, producing thick, white fumes of antimony 
or arsenic chloride as the case may be. 

If a morsel of phosphorus, contained in a deflagrating spoon, 
be plunged into a jar of chlorine, the phosphorus melts and 
inflames spontaneously, and the sides of the jar become covered 
with a yellow, crystalline deposit of phosphorus pentachloride, 
PCP. 

But the affinity of chlorine is most strikingly manifested by 
its action on hydrogen and hydrogen compounds. 



CHLORINE. 115 

When a lighted taper is applied to a mixture of equal vol- 
umes of chlorine and hydrogen, the two gases unite instantly 
and explosively. Such a mixture will also explode violently 
on being exposed to direct sunlight ; the rays of the sun may 
even be replaced by the flame of magnesium or that of carbon 
disulphide. 

So great is the affinity of chlorine for hydrogen that it de- 
composes all hydrogen compounds, except hydrochloric and 
hydrofluoric acids. When it is dissolved in water, it slowly 
decomposes that liquid under the influence of sunlight, com- 
bining with the hydrogen and setting the oxygen at liberty. 

If a tube filled with an aqueous solution of chlorine be 
inverted over the pneumatic trough and exposed to direct sun- 
light, small bubbles of gas will be seen to rise through the liquid 
and collect at the top of the tube. This is the oxygen result- 
ing from the decomposition of the water. 

At a red heat, the vapor of water is rapidly decomposed by 
chlorine ; hydrogen sulphide gives up its hydrogen to chlorine 
at ordinary temperatures. 

All organic substances contain hydrogen ; they are therefore 
generally modified, and often destroyed by the action of chlorine. 
Coloring matters of organic origin are bleached. 

Experiment. — If a solution of chlorine be added to a solu- 
tion of litmus, sulphate of indigo, or ink, the intense colors 
peculiar to these substances disappear, giving place to a pale 
yellow or brown tint. This eff'ect is due to the more or less 
profound decomposition which these coloring matters undergo 
by reason of the removal of a certain portion of their hydro- 
gen in the form of hydrochloric acid. 

This bleaching property of chlorine is of great service in the 
arts. 

A wax taper will burn in chlorine gas with a red, smoky 
flame. The hydrogen of the wax combines with the chlorine, 
while the carbon is set free as smoke. A piece of paper satu- 
rated with oil of turpentine takes fire spontaneously when 
introduced into a jar of chlorine, producing a dense cloud of 
smoke ; the turpentine contains only carbon and hydrogen the 
latter is attacked by the chlorine, the former being set free. 

Chlorine is also an efficacious disinfectant. It decomposes 
hydrogen sulphide. It destroys odorous matters of organic 
origin, the effluvia resulting from putrid fermentation, and 
the miasms which are sometimes diffused in the air. It 



116 ELEMENTS OF MODERN CHEMISTRY. 

is employed to disinfect privjs, etc., and to purify the air in 
certain epidemics. 

The bleaching properties and disinfecting properties of 
chlorine are due to the same cause, — its powerful affinity for 
hydrogen. 

HYDROCHLORIC ACID. 

Density compared to air 1.247 

Density compared to hydrogen 18. 

Molecular weight HCl ^= 36.5 

Hydrochloric acid exists among the gaseous products disen- 
gaged by volcanoes. 




Preparation. — Fragments of fused common salt are intro- 
duced into a flask fitted with a safety-tube and delivery-tube, 
like that for the preparation of chlorine, and concentrated sul- 
phuric acid is added. Hydrochloric acid gas is disengaged, and 



HYDROCHLORIC ACID. 



117 



may be collected over mercury. Sodium acid sulphate remains 
in the retort. 



H^SO* + NaCl = NaHSO^ + 

Sodium chloride. Sodium acid sulphate. 



HCl 



In the arts, the operation is conducted in cast-iron cylinders 
or furnaces (Fig. 41), at a high temperature. Under these 
conditions, one molecule of sulphuric acid acts upon two mole- 
cules of sodium chloride, yielding sodium neutral sulphate, 
and two molecules of hydrochloric acid. 

H^'SO* -f 2NaCl = Na^SO* + 2HC1 

Sodium sulphate. 

The hydrochloric acid gas evolved is passed into stoneware 
bottles, C, C, C", containing water. It is thus dissolved, 
and the solution obtained constitutes the muriatic acid of com- 
merce. 

A solution of hydrochloric acid may be prepared in the 
laboratory by passing the gas through water contained in a 
series of Wolff* bottles surrounded by cold water, the contents 
of the first bottle being rejected (Fig. 42). 




Fig. 42. 



Composition of Hydrochloric Acid. — The composition of 
this gas may be deduced from the following experiments : 



118 



ELEMENTS OF MODERN CHE3IISTRY. 




1. A bottle, B (Fig. 43), the neck of which is adapted by 
grinding with emery to the flask A, is filled with dry chlorine ; 

A, which has exactly the same capacity as 
the bottle, is filled with dry hydrogen ; the 
two vessels are then fitted together, and by 
means of the ground joint are hermetically 
sealed. The apparatus is now abandoned 
for a time to diffuse light, and as the two 
gases slowly mix they combine. The union 
is completed by exposing the apparatus to 
direct sunlight. When the tint of the 
chlorine has entirely disappeared, the two 
vessels are separated under the surface of 
mercury, and it is found that no change in 
volume has taken place. The chlorine and 
hydrogen have both disappeared to form 
hydrochloric acid, which occupies precisely 
the same volume as the two primitive gases. Consequently 2 
volumes of hydrochloric gas contain 1 volume of chlorine and 
1 volume of hydrogen ; and if the weight of one volume of 
hydrogen (unity) be added to that of one volume of chlorine 
(its density compared to hydrogen as unity), the sum will be 
the weight of two volumes of hydrochloric acid, and will also 
represent the weight of the molecule. 

Densities com- 
pared to H. 
Weight of 1 volume of hydrogen .... 1 
Weight of 1 volume of chlorine .... 35.5 
Weight of 2 volumes of hydrochloric acid 36.5 2.5093 

2. Two volumes of hydrochloric acid gas are passed into a 
bent tube over mercury (Fig. 4-1), and a small piece of sodium 

is passed up into the bulb and 
heated by the flame of a spirit- 
lamp. The sodium combines 
with the chlorine setting the 
hydrogen at liberty, and after 
the experiment one volume of 
hydrogen remains in the tube. 
This second experiment con- 
firms the first, both proving 
that hydrogen and chlorine 
unite in equal volumes, and 
without condensation, to form 



Densities com- 
pared to Air. 
0.0693 
2.44 




Fig 



HYDROCHLORIC ACID. 



119 



hydrochloric acid. One volume of hydrochloric acid contains 
half a volume of hydrogen and half a volume of chlorine, but 
we cannot admit that the atoms of these elements are divided 
into two in the formation of hydrochloric acid ; such a sup- 
position would be contrary to all ideas of atoms, which repre- 
sent the smallest particles of an element that can exist in a 
compound. It is more natural to conclude that two vol- 
umes of chlorine and two volumes of hydrogen react together 
in the formation of hydrochloric acid. Two volumes of 
chlorine contain two atoms, constituting one molecule of chlo- 
rine. In the same manner two volumes of hydrogen contain 
two atoms, constituting one molecule of hydrogen. 



CI 


CI 



H 


H 



2 volumes or 1 molecule of 
chlorine = ClCl. 



2 volumes or 1 molecule of 
hydrogen = HII. 



It is these molecules which are separated into two when 
chlorine combines with hydrogen : they exchange their atoms, 
and from the exchange, which is a double decomposition, there 
result two molecules of hydrochloric acid, which occupy pre- 
cisely the same volume as the two molecules of the simple gases. 



CI 


CI 


+ 


H 


H 


=. H 


CI 


+ 


H 


CI 



2 vols, of chloiine + 2 vols, of hydrogen ^= 2 vols, of hydro- + 2 vols, of hydro- 
chloric acid chloric acid. 

We encounter here again the notion that certain elements in 
the free state are composed of molecules, each of which con- 
tains two atoms of the same kind. The force which unites 
them is not different from affinity. It is affinity which unites 
chlorine to chlorine in the molecule of that element ; hydrogen 
to hydrogen in the molecule of free hydrogen (Gerhardt). 
When, however, these two molecules are brought together, the 
affinity of chlorine for hydrogen preponderates, and brings about 
an exchange, a double decomposition. 

Physical Properties. — Hydrochloric acid is a colorless gas 
having a pungent odor. It forms thick white fumes in the air 
by condensing the atmospheric moisture. It may be liquefied 
by a pressure of 40 atmospheres. 

It is One of the most soluble of gases in water. If a jar 
filled with this gas and inverted on a plate containing mercury 



120 ELEMENTS OF MODERN CHEMISTRY. 

SO that the mouth is sealed, be depressed in the pneumatic 
trough, and the plate be then quickly removed, the water im- 
mediately rushes into the jar as it would into a vacuum. The 
shock of the column of water is sometimes sufficient to break 
the jar. 

One volume of water at 0° dissolves 500 volumes of hydro- 
chloric acid; at ordinary temperatures, about 480 volumes. 
The water becomes heated and increases in volume. The cold 
saturated solution has a density of 1.21 and contains 42.4 
per cent, by weight of the dry gas. It is a colorless liquid, 
giving off white fumes. When it is heated, it loses a large 
quantity of the gas which it holds in solution, but the whole 
of the gas is not disengaged, and when the temperature reaches 
110° the liquid distils without further loss of gas. A dilute 
hydrochloric acid is thus obtained, having a uniform density of 
1.10 (Bineau). 

Chemical Properties. — Hydrochloric acid is an energetic 
acid ; it strongly reddens litmus-paper. It is not decomposable 
by heat, but is partly decomposed by a series of electric sparks. 
All of the metals which decompose water also decompose hy- 
drochloric acid with the liberation of hydrogen and the for- 
mation of a chloride. Such metals are sodium, zinc, iron, 
aluminium, tin, etc. 

Hydrochloric acid decomposes the metallic oxides and hy- 
drates with the formation of water and a chloride. 

If hydrochloric acid be added in small quantities to a con- 
centrated solution of potassium hydrate, the liquid becomes 
heated and deposits potassium chloride as a crystalline powder. 

HCl + KOH = KCl -f WO 

Potassium hydrate. Potassium chloride. 

Hydrochloric acid is then a true acid although it contains no 
oxygen, for it contains an atom of hydrogen that is replaceable 
by an atom of metal. In its action upon potassium hydrate it 
resembles nitric acid, for this acid also contains one atom of 
hydrogen, which is replaceable by an atom of metal. 

HNO^ + KOH = KNO^ -f H^O 

Nitric acid. Potassium nitrate. 

It is seen that the acids are compounds containing a strongly 
electro-negative atom or group of atoms, united with hydrogen, 
which hydrogen can be replaced by a metal. In nitric acid, 
H(NO^), the group NO'^ plays the part taken by chlorine in 



OXYGEN COMPOUNDS OF CHLORINE. 



121 



hydrochloric acid ; like the chlorine, it renders the hydrogen 
replaceable by a metal. 

The action of hydrochloric acid upon the metallic oxides is 
analogous to that which it exerts upon the hydrates. 

If a current of hydrochloric acid be passed over mercuric 
oxide contained in a tube (Fig. 45), the oxide becomes heated, 

n 




Fig. 45. 

and is converted into a white powder which is mercuric chlo- 
ride ; at the same time water is formed and condenses in the 
bulb. 

HgO + 2HC1 = HgCP + WO 

Mercuric oxide. Mercuric chloride. 

OXYGEN COMPOUNDS OF CHLOKINE. 

With oxygen, chlorine forms compounds which may be an- 
hydrous or hydrated ; the latter are acids. 
The oxides are : 

Ilypochlorous oxide .......... CPO 

Chlorous oxide C1203 

Chlorine peroxide CPO* 

The acids are : 

Hypochlorous acid HCIO 

Chlorous acid * . . . HCIO^ 

Chloric acid HC103 

Perchloric acid HCIO* 

F 11 



122 



ELEMENTS OF MODERN CHEMISTRY. 



HYPOCHLOEOUS OXIDE AND ACID. 

Hypoclilorous oxide is prepared by passing a current of dry 
chlorine over mercuric oxide contained in a tube surrounded 
by cold water, and may be condensed in a long-necked matrass 
placed in a freezing mixture (Fig. 46). 



HgO + 

Mercuric oxide. 



2C1= 



= HgCl^ + 

Mercuric chloride. 



CPO 




Fig. 46. 



The oxide condenses as a brown-red liquid, boiling at 20°. 
Above that temperature it is a reddish-yellow vapor, having a 
density of 2.977, or, compared to hydrogen as unity, 43.5. 
Two volumes of this vapor contain two volumes of chlorine 
and one volume of oxygen, a composition represented by the 
formula CPO. 

Hypoclilorous oxide is a dangerous body, and cannot be kept 
for more than a few hours without spontaneous decomposition ; 
its vapor frequently explodes. 

In combining with the elements of water, hypochlorous oxide 
forms hypoclilorous acid, the solution of which is almost color- 
less. 



CI 
CI 



^ + h}<> = Cl}^ + H> 



CHLOROUS OXIDE. 123 

Preparation of Hjrpochlorous Acid. — 1. A solution of 
hypoclilorous acid may be prepared by agitating mercuric 
oxide with water in jars filled with chlorine gas. The water 
will then contain hypoclilorous acid and mercuric chloride, and 
there remains a brown powder, which is mercury oxychloride 
(Balard). 

2. A current of chlorine is passed through water holding 
recently-precipitated calcium carbonate in suspension. The 
latter disappears, carbonic acid gas is disengaged, and the 
water becomes charged with calcium chloride and hypochlorous 
acid. The mixture is distilled, and the acid which passes with 
the water is condensed in a cooled receiver (Williamson). 

CaCO^ + 2CP + WO == CO^ -f CaCP + 2HC10 

Calcium Carbon Calcium Hypochlorous 

carbonate. dioxide. chloride. acid. 

Properties of Hypoclilorous Acid. — Concentrated hypo- 
chlorous acid is a dark-yellow Jiquid, having the peculiar smell 
of chlorinated lime or bleaching-powder. It is very caustic, 
and rapidly destroys the skin ; its bleaching power is very en- 
ergetic, double that of the chlorine it contains. Hydrochloric 
acid decomposes it into chlorine and water. 

HCIO -f HCl = CP + H^O 
CHLOROUS OXIDE. 

Chlorous oxide is formed when potassium chlorate is decom- 
posed by dilute nitric acid in the presence of a body capable 
of uniting with oxygen, such as arsenious oxide. At a gentle 
heat a greenish gas is disengaged which does not liquefy at a 
temperature of — 20°. This gas is not stable; above 5*7° it 
decomposes with explosion into chlorine and oxygen. 

It dissolves in water, forming a dark golden-yellow solution 
containing chlorous acid, a body quite unstable itself. 

CPO« + H^O = 2HC10' 

Chlorous oxide. Chlorous acid. 



124 



ELEMENTS OP MODERN CHEMISTRY. 



CHLORINE PEROXIDE. 




Fig. 47. 



3KC10^ + 

Potassium 
chlorate. 



:h^SO* 



: KCIO* 

Potassinm 
perclilorate 



This compound, which was 
discovered by Sir Humphry 
Davy, is prepared by the ac- 
tion of concentrated sulphuric 
acid upon fused potassium 
chlorate. The salt is finely 
pulverized and added in small 
quantities to sulphuric acid 
cooled to — 10°. The pasty 
mass is then introduced into 
a small test-tube fitted with a 
delivery-tube (Fig. 47), and 
is gently heated in a water- 
bath ; the gas disengaged is 
collected in dry jars by down- 
ward displacement. 

-I- 2KHS0* + H^O + CPO* 

Potassium acid 
sulphate. 



Chlorine peroxide is a yellow gas having a sweetish aromatic 
odor. At — 20° it condenses to an orange-red liquid. Its den- 
sity in the gaseous state is 33.75 (hydrogen being unity). This 
density is anomalous, and indicates that at the instant the liquid 
Cl'^0* assumes the gaseous state it is dissociated into two more 
simple molecules, ClO^ -f- ClO^, which occupy four volumes. 



CP 



0* 



is resolved into 



CI 


0^ 


+ 


CI 


0^ 



The density of gaseous chlorine peroxide is then only half 
that required by the formula Cl'^O*. 

If one volume of hydrogen weighs 1, 

one volume of CPO* ought to weigh .... 67.5. 
But it weighs only 33.75, 

which proves that CPO* in the gaseous state occupies four 
volumes instead of two. 

These four volumes contain, 2 volumes of CI, weighing 2 >^ 35.5 = 71 
4 volumes of 0, weighing 16 X 4 = 64 

135 
135 
Weight of one volume, or density, compared to H . . = -— = 33.75 



CHLORIC ACID— PERCHLORIC ACID. 125 

Chlorine peroxide is a dangerous body; it sometimes de- 
composes spontaneously with violent explosions. 

It is soluble in water, and the solution may be prepared by 
heating on a water-bath a mixture of equal parts of oxalic acid 
and potassium chlorate. Carbonic acid and chlorine peroxide 
gases are disengaged, and may be passed into water. 

Chlorine peroxide is absorbed by alkaline solutions with the 
formation of a chlorate and a chlorite. 

2K0H + CPO* = KCIO^ + KCIO^ + H^O 

Potassium hydrate. Potassium chlorate. Potassium chlorite. 



CHLORIC ACID. 
HC103 

This acid is formed by the spontaneous decomposition of 
solutions of hypochlorous and chlorous acids and chlorine per- 
oxide. 

It may be prepared by treating barium chlorate with dilute 
sulphuric acid. Barium sulphate precipitates, and is removed 
by filtration, and the solution of chloric acid is concentrated by 
evaporation in vacuo. 

Chloric acid is a syrupy liquid, ordinarily of a yellow color ; 
it is not very Stable ; at a temperature of 40° it commences to 
decompose, and at a higher temperature it is resolved into per- 
chloric acid, chlorine, oxygen, and water. It has extremely 
energetic oxidizing properties ; when concentrated, it at once 
inflames sulphur, phosphorus, alcohol, and paper. It oxidizes 
sulphurous and phosphorous acids and hydrogen sulphide. 
With hydrochloric acid it forms water and chlorine. 

HCIO^ + 5HC1 = 3H?0 -f 3CP 



PERCHLORIC ACID. 

HCIO* 

This is the most rich in oxygen of all the chlorine acids, 
and it is a curious circumstance that it is also the most stable. 

It may be prepared by distilling potassium perchlorate with 
concentrated sulphuric acid. Roscoe obtains it by distilling 
chloric acid, which is prepared by decomposing a solution of 
potassium chlorate by hydrofluosilicic acid. The insoluble po- 

11* 



126 ELEMENTS OP MODERN CHEMISTRY. 

tassium fluosilicate is separated by filtration, the filtered liquid 
is concentrated until white fumes appear, and then the distil- 
lation is commenced. The product must be rectified after 
being freed from the chlorine which is formed at the same 
time. 

The perchloric acid thus obtained is a heavy, oily, colorless 
liquid, resembling concentrated sulphuric acid. It still con- 
tains water, which may be removed by distillation with four 
times its weight of concentrated sulphuric acid. At about 
100° dense vapors pass and condense into a very mobile, yellow 
liquid ; this is the perchloric acid HCIO* ; the temperature 
then rises, and at 200° a liquid passes which solidifies to a 
crystalline mass on cooling. These crystals are a hydrate, 
HCIO* + H^O. 

The pure or normal perchloric acid has a density of 1.782 
at 15.5°. When brought into contact with water, it combines 
with that liquid, producing a hissing noise. Its oxidizing 
powers are so energetic that it explodes on contact with paper, 
wood, or charcoal. It may be mixed with alcohol, but with 
ether it explodes. It cannot be distilled. The hydrate 
HCIO* + IPO melts between 50 and 51°. 

CHLORIDES OF SULPHUR. 

When a current of dry chlorine is passed over sulphur heated 
in a retort, a liquid condenses in the receiver which fumes in 
the air, has a yellow color, and an irritating, fetid odor. This 
is sidphinous cliloride, S^CP. In order that this compound 
may be formed, the sulphur must be maintained in excess, and 
the operation must be stopped before it has all disappeared. 
The product is purified by rectification, that part being collected 
which passes at 139°. 

When chlorine is passed for several hours tlirough the 
chloride of sulphur just described, the yellow color of the 
latter changes to deep red. The liquid obtained is mobile, 
fumes in the air, and continually disengages chlorine. It can- 
not be distilled without decomposition. The product which 
passes is at first red, but afterwards assumes a lighter color, and 
when the temperature reaches 139° there remains in the retort 
only sulphurous chloride, S'CP. 

The red liquid has a composition which corresponds to the 
formula S'^Cl*. It is called perchloride of sulphur. Carius 



BROMINE. 127 

regards it as a mixture of the chloride S^CP with a tetra- 
chloride SCI*, corresponding to sulphurous oxide. 

SO^ sulphur dioxide. 
SCI* sulphur tetrachloride. 

This tetrachloride has been recently isolated by Michaelis, 
but it can only exist at a low temperature ; it decomposes into 
chlorine and sulphurous chloride, S'^CP, as soon as it is removed 
from the freezing mixture where it has been condensed. 

The chlorides of sulphur are employed in vulcanizing 
caoutchouc. 



BROMINE. 

Vapor density compared to air . . . 6.393 

Vapor density compared to hydrogen . 77.9 (nearly 80) 

Atomic weight Br =^80. 

Bromium was discovered by Balard in 1826. 

Preparation. — It is obtained by decomposing potassium 
bromide by manganese dioxide and sulphuric acid. Potassium 
sulphate and manganese sulphate are formed, and the bromine 
is liberated. 

2KBr + MnO^ + 2H^S0* =- K^SO* -j- MnSO* + 2H^0 + Br^ 

Potassium Manganese Potassium Manganese 

bromide. dioxide. sulphate. sulphate. 

The operation is conducted in a tubulated retort, heated on 
a sand-bath, and the bromine is condensed in a cooled receiver 
fitted to the retort by the aid of an adapter. 

The potassium bromide may be replaced by magnesium 
bromide, which exists in the mother-liquors of salt-springs. 
In this case magnesium sulphate is formed. The mother- 
liquors of the soda varech from which the iodine has been ex- 
tracted are also employed for the preparation of bromine. 

Properties. — Bromine is a dark-red liquid, which solidifies 
at —7.3°. Its density at 15° is 2.99. It boils at 63°, and at 
ordinary temperatures gives off red, irritating vapors, for its 
vapor tension is considerable even in the cold. It stains the 
skin yellow, and immediately corrodes the tissues. It dissolves 
in about 33 times its weight of water at 15°, forming an orange- 
red solution. At a low temperature it combines with water, 
forming a crystalline hydrate, Br^ -\- IOH'^0, analogous to that 
formed by chlorine. 



128 ELEMENTS OF MODERN CHEMISTRY. 

Bromine dissolves in carbon disulphide, in chloroform, and in 
ether. 

Experiment. — A small quantity of solution of potassium 
bromide is introduced into a long tube, closed at one end, and 
the tube is then nearly filled with chlorine- water ; when the two 
solutions are mixed, the liquor assumes an orange-red color 
from the liberation of the bromine. The tube is now filled up 
with ether and agitated briskly, the open end being closed with 
the finger. The ether passes through the aqueous solution 
and dissolves out all of the bromine, assuming at the same time 
a dark-red color. 

The affinity of bromine for hydrogen is powerful, but not as 
energetic as that of chlorine. Like chlorine, it has remarkable 
bleaching properties. 

HYDROBROMIC ACID. 

Density compared to air 2.73 

Density compared to hydrogen 40.5 

Molecular weight HBr =81. 

Preparation. — This gas is prepared by the action of water 
upon phosphorus tribromide. 

Phosphorus tribromide. 3 molecules water. Phosphorous acid. 

The operation may be conveniently conducted in a doubly- 
curved tube (Fig. 48). Into the long branch CD fragments of 
phosphorus are introduced, carefully separated from each other 
by moistened broken glass. The bromine is introduced into 
the bend A. The shorter end is then corked, a delivery-tube 
adapted to the end D, and the bromine is gently heated until it 
boils. The vapor comes into contact with the phosphorus and 
forms phosphorus tribromide, but this is at once decomposed 
by the water into phosphorous acid and hydrobromic acid. 
The latter may be collected in jars over the mercury-trough. 

Amorphous phosphorus may be advantageously employed in 
this operation, and the process conducted as directed for hydri- 
odic acid (Personne). 

Properties. — Hydrobromic acid is a colorless gas, producing 
dense white fumes in the air. A litre of this gas weighs 3.547 
grammes. It liquefies at — 73°, and may be solidified at a 
lower temperature. It is formed by the union of equal volumes 



OXYGEN ACIDS OF BROMINE. 



129 



of bromine vapor and hydrogen without condensation, so that 
its composition corresponds to that of hydrochloric acid. It 
is very soluble in water ; its concentrated solution fumes in the 
air, and is very corrosive. 

Chlorine decomposes hydrobromic acid, setting free the 
bromine. 




Fig. 4S. 

OXYGEN ACIDS OF BROMINE. 

There are known three bromine oxygen acids : 

Hypobromous acid, HBrO. 
Bromic acid, HBrO^ 
Perbromic acid, HBrO*. 

They correspond to hypochlorous, chloric, and perchloric 
acids. 

Hjrpobromous Acid, HBrO. — When mercuric oxide is 
agitated with an aqueous solution of bromine, a yellowish 
liquid is obtained which contains hypobromous acid, and can 
be distilled in vacuo. W. Dancer has obtained this acid by the 
action of bromine upon silver oxide suspended in water. 

2Br^ -f Ag^O -h H^O = 2AgBr -f 2HBrO 

Silver oxide. Silver bromide. 

In this process it is necessary to operate rapidly and avoid 



130 ELEMENTS OF MODERN CHEMISTRY. 

the contact of an excess of silver oxide with the hypobromous 
acid, as the latter would be destroyed by the oxide with evolu- 
tion of oxygen. 

2HBrO + Ag'^0 = 2AgBr -f H^O + 0^ 

The solution of hypobromous acid has a yellow color and 
bleaching properties analogous to those of hypochlorous acid. 

Bromic Acid, HBrO\ — Potassium bromide and potassium 
bromate are formed by the action of bromine upon a concen- 
trated solution of potassium hydrate. This reaction is similar 
to that of chlorine upon potassa. 

Kammerer recommends the preparation of bromic acid by 
the action of chlorine upon bromine in presence of water. 

5CP + Br^ + 6ffO :::= lOHCl + 2HBrO" 

The hydrochloric acid is driven out by evaporation, and 
bromic acid remains in the form of a liquid that cannot be con- 
centrated to a syrupy consistence without partial decomposition. 

Perbromic Acid, HBrO*. — Kammerer has obtained this 
acid by decomposing perchloric acid with bromine : chlorine is 
disengaged. After concentration on a water-bath, the per- 
bromic acid remains as a colorless oily liquid. It is relatively 
stable, as are the corresponding chlorine and iodine acids. Like 
them, it resists the reducing action of sulphurous acid and 
hydrogen sulphide. 



IODINE. 



Vapor density compared to air . . . 8.716 

Vapor density compared to hydrogen . 125.1 (nearly 127) 

Atomic weight I = 127. 

Iodine was discovered by Courtois in 1811, and was studied 
by Gay-Lussac in 1813 and 1814. 

Natural State. — Iodine is widely disseminated in nature. 
It is found in the mineral kingdom combined with various 
metals, such as potassium, sodium, calcium, magnesium, silver, 
mercury. The alkaline iodides exist in small quantity in sea- 
water, in a great number of salt-springs, and in certain rock- 
salts. The sodium nitrate found native in Chili contains traces 
of sodium iodate, and the mother-liquors from which the nitrate 
has been deposited contain enough iodate to be profitably 
employed for the preparation of iodine. The ashes of certain 



IODINE. 131 

sea-plants, such as the algae and fuci, are the most abundant 
sources of iodine. 

Preparation. — The ashes of sea-weeds, called kelp, are ex- 
hausted with water and the solution concentrated. Various 
salts, such as sodium and potassium sulphates and chlorides 
and sodium carbonate, are deposited, and the potassium iodide, 
which is contained in smaller quantity than these salts, remains 
in the mother-liquor. 

A regulated current of chlorine is passed into this solution 
as long as it continues to set free iodine, which is deposited as 
a pulverulent, black precipitate. An excess of chlorine must 
be avoided, as this would redissolve a portion of the iodine, 
forming iodine chloride. 

Another process consists in mixing the mother-liquor with 
ordinary nitric acid and gently heating the mixture. The alka- 
line iodide is decomposed by the acid, a nitrate is formed, red 
vapors are disengaged, and iodine is set free. 

4HN0^ + 2KI = 2KN0^ + 2N0^ + 2W0 -f V 

Nitric Potassium Potassium Nitrogen 

acid. iodide. nitrate. peroxide. 

The precipitated iodine is collected, drained, and after drying 
is sublimed in stoneware vessels. 

The same process that has been described for the manufacture 
of bromine from potassium bromide may also be applied for the 
extraction of iodine. It consists in treating the iodide with 
manganese dioxide and sulphuric acid. 

Properties of Iodine. — The iodine obtained by sublimation 
occurs as scales or crystalline plates, having a brilliant, dark 
bluish-gray surface, and a density of 4.948 at 17°. It may be 
obtained crystallized in rhombic octahedra by exposing to the 
air a solution of hydriodic acid. 

Iodine melts at 107°. It boils at about 175°, but volatilizes 
sensibly at ordinary temperatures. Its vapor has an intense 
rich violet color. A litre of this vapor weighs 11.32 grammes. 

Iodine is but very slightly soluble in water ; one part of 
iodine requires 7000 parts of water for its solution, but com- 
municates a light-brown color to the whole of that liquid. 
Alcohol and ether dissolve iodine freely, forming dark-brown 
solutions. Carbon disulphide, benzine, and chloroform also 
dissolve it, assuming a beautiful violet color. 

Experiment. — If a few drops of chlorine-water be added to 
a very dilute solution of potassium iodide, the chlorine will 



132 ELEMENTS OF MODERN CHEMISTRY. 



combine with the potassium, displacing the iodine, which will 
color the liquid brown ; if now the solution be agitated with a 
small quantity of chloroform, the latter will take up all of the 
iodine, assuming a violet color. 

Iodine strikes an intense blue color with starch. The reac- 
tion is very delicate and permits the detection of the smallest 
trace of free iodine. 

Experiment. — If a few drops of a solution of potassium 
iodide be added to a solution of starch, no coloration takes 
place, because the iodine is in combination ; but if a drop or 
two of chlorine-water be added, the iodine will be set free, and 
combining with the starch will at once produce the character- 
istic blue color. An excess of chlorine will again destroy the 
color. 

HYDEIODIC ACID. 

Density compared to air 4.443 

Density compared to hydrogen 64.1 

Molecular weight HI -=128. 

Preparation. — Hydriodic acid is prepared by the action of 
iodine upon phosphorus in presence of water; phosphorus 
triiodide is first formed, and this is decomposed into phos- 
phorous acid and hydriodic acid. 



PP + g'[0' = ^ajC + 

Phosphorus 3 molectiles Phosphorous 

triiodide. of water. acid. 



SHI 



Amorphous phosphorus in powder is introduced into a glass- 
Stoppered retort the neck of which is soldered to the delivery- 
tube (Fig. 49), and covered with a layer of water ; the iodine 
is then added, and on the application of a gentle heat a regular 
current of hydriodic acid is obtained. The gas may be col- 
lected, like chlorine, by downward displacement in dry jars. 

Properties. — Hydriodic acid is a colorless gas producing 
white fumes in the air. It may be condensed to a yellow 
liquid by strong pressure or intense cold, and can even be solid- 
ified. Dry oxygen decomposes it at a high temperature, water 
being formed and the iodine being set at liberty. 

If a lighted taper be applied to a mixture of hydriodic acid 
and oxygen, the violet vapor of the iodine set free is instantly 
apparent. 

This decomposition of hydriodic acid by oxygen takes place 
at ordinary temperatures in the presence of water. A solution 



HYDRIODIC ACID. 



133 



of hydriodic acid exposed to the air rapidly becomes brown, 
and after a time deposits crystals of iodine. 

Solution of hydriodic acid is prepared by passing the gas into 
water cooled to 0°. It may also be made by passing a current 
of hydrogen sulphide through water holding iodine in suspen- 
sion ; hydriodic acid is formed, and sulphut is precipitated. 
H^S +• r = 2HI + S 

The saturated solution of hydriodic acid has a density of 
1.7, and fumes in the air. When freshly prepared, it is color- 




FiG. 49. 

less ; when heated, it loses part of its gas, and finally distils 
unaltered at 126°. The saturated solution contains 57.7 per 
cent, of the dry acid. 

Chlorine and bromine at once decompose hydriodic acid, 
combining with the hydrogen and setting free the iodine. The 
experiment may be made by pouring a few drops of bromine 
into a jar filled with hydriodic acid gas, when the appearance 
of a violet vapor immediately indicates the liberation of iodine. 

Potassium, zinc, iron, mercury, and silver decompose hydri- 
odic acid, but with unequal energies, setting free the hydrogen. 

12 



134 ELEMENTS OF MODERN CHEMISTRY. 

Sulphuric acid also decomposes it, and is itself reduced to sul- 
phurous oxide. 

H^SO* + 2HI = 2H20 + SO' + P 

Nitric acid is still more readily reduced by hydriodic acid. 

2HN0' + 2HI = 2H'0 + 2N0' + P 

Nitric acid. Nitrogen peroxide. 

IODINE OXIDES AND OXYGEN ACIDS. 

Among the compounds of iodine and oxygen, iodic and peri- 
odic oxides are the only ones known with certainty. The ex- 
istence of the other oxides, although possible and even probable, 
has not been fully demonstrated. These compounds would form 
the following series : 

Hypoiodous oxide PC 

lodous oxide PO^ 

Iodine peroxide I'^O* 

Iodic oxide l^Q^ 

Periodic oxide 1^07 

In combining with water, these oxides form acids ; it is only 
necessary to describe here iodic and periodic acids. 
PO^ -^ H'^0 = 2HI0^2 molecules iodic acid. 
PO' + H'O = 2HIO*,2 molecules periodic acid. 

IODIC ACID. 
HI03 = I02(0H) 

Iodic acid is formed when iodine is submitted to the action 
of energetic oxidizing agents, such as concentrated nitric acid 
or a mixture of nitric acid and potassium chlorate. It is also 
formed by the action of an excess of chlorine on iodine in 
presence of water. 

P + 5CP -f 6H^0 = lOHCl + 2HI0^ 

Preparation. — Iodic acid may be conveniently prepared by 
heating iodine and potassium chlorate with dilute nitric acid. 
The oxygen of the chlorate oxidizes the iodine to iodic acid, 
and on adding barium nitrate to the liquid, barium iodate is 
precipitated. The latter salt is decomposed by sulphuric acid ; 
iodic acid is set free in the solution, and barium sulphate is 
precipitated ; the filtered solution is concentrated by evapora- 
tion in vacuo. 

Properties, — Iodic acid is solid, and crystallizes in hex- 
agonal tables. When heated to 170° it loses water and is 



PERIODIC ACID. 135 

converted into iodic oxide, and at a red heat the latter is 
decomposed into iodine and oxygen. 

It is seen that iodic acid is much more stable than its ana- 
logue, chloric acid ; nevertheless it is easily reduced by bodies 
avid of oxygen. 

If sulphurous acid be added to a solution of iodic acid, a 
precipitate of iodine is formed instantly, but an excess of sul- 
phurous acid redissolves the precipitate, part of the water being 
decomposed and hydriodic and sulphuric acids being formed. 

Iodic acid is also decomposed by hydriodic acid. If a solu- 
tion of iodic acid be poured into a solution of starch, no color- 
ation appears, but the characteristic blue color is at once 
developed on adding a drop of hydriodic acid. 
HIO=^ + 5HI = SH^O + SP 

PERIODIC ACID. 

This acid has been obtained from disodic periodate, a salt 
which is precipitated when a current of chlorine is passed 
through a solution of sodium iodate mixed with sodium hydrate. 

NalO^ + 3NaOH + CP =^ 10^ | ^\wO + 2NaCl 

Sodium iodate. Sodium hydrate. Disodic periodate. Sodium chloride. 

The crystalline precipitate is dissolved in nitric acid, and 
lead nitrate is added to the solution ; lead periodate is precipi- 
tated, and this salt is exactly decomposed by sulphuric acid ; 
the liquid is filtered to separate the lead sulphate, and evapo- 
rated at a gentle heat. The periodic acid crystallizes out in 
colorless, deliquescent, rhombic prisms, fusible at 130°. These 
crystals contain 11=^10^ -f H'O. At 160° they lose water and 
are converted into a white mass of periodic oxide. 

2(H^I0^H^0) = rO^ + 5H^0 
Between 180 and 190° periodic oxide abandons oxygen, and 
is converted into iodic oxide, PO^. 

Periodic acid forms several varieties of salts. 

There is a diargentic periodate, 10^ \ tt^ ,H^0 = 
COAo'T'^ ( ■"• 

IO^<QTT ^ + H^O, corresponding to the disodic salt before 

mentioned ; but there is also a silver periodate, AglO*, to 
which corresponds an acid, HIO*, having a composition analo- 
gous to that of perchloric acid, but which has not yet been 
obtained. 



136 ELEMENTS OF MODERN CHEMISTRY. 

Analogy between Chlorine, Bromine, and Iodine. — Chlo- 
rine, bromine, and iodine present a striking analogy in their 
chemical properties, and this analogy is seen in all of their 
compounds. They combine with hydrogen, atom for atom, 
forming the acids 

HCl 

HBr 

HI 

and it is seen that the atoms of chlorine, bromine, and iodine 

are equivalent to each other and to an atom of hydrogen ; each 

of these elements is monatomic. 

Their affinities for hydrogen are far from being equal ; in this 
respect chlorine is more powerful than bromine, and bromine 
than iodine. The contrary has been noticed regarding their 
affinities for oxygen, for the oxygen acids of iodine are more 
stable than those of chlorine. 

The analogy between these three elements is followed out 
in the constitution of their oxides and acids, and in their com- 
binations with the metals. The chlorides, iodides, and bro- 
mides possess in general the same constitution, and it is to be 
remarked that the greater part of these binary compounds are 
soluble in water and are crystallizable like salts, of which they 
otherwise present the characters. Hence the name halogen 
bodies, which was applied by Berzelius to this group of elements, 
to indicate that they form salts in combining with the metals. 



FLUORINE. 

Fl = 19. 
This is a body belonging to the same group just considered, 
and having a chemical energy much superior to that of chlorine. 
It exists in the common mineral fluor spar, which is a combina- 
tion of fluorine and calcium. But fluorine has never been 
isolated ; it attacks all vessels, and it would be necessary to 
have apparatus and vessels cut from fluor spar in order to con- 
tain it. There is a compound of fluorine and hydrogen. 

HYDROFLUORIC ACID. 

Molecular weight HFl =20 

This compound is prepared by decomposing powdered cal- 
cium fluoride with sulphuric acid. 

CaFP + H^SO* = CaSO* + 2HF1 

Calcium fluoride. Calcium sulphate. 



HYDROFLUORIC ACID. 



IST 



The operation is conducted in a leaden retort, to which is 
adapted a receiver of the same metal surrounded hj a freezing 
mixture (Fig. 50). 
The hydrofluoric 
acid condenses as 
a very acid liquid, 
which fumes strong- 
ly in the air. Its 
density is 1.06. In 
this state it still re- 
tains water ; but 
Fremy obtained it 
anhydrous by de- =f| 
composing dry hy- 
drofluoride of fluor- 
ide of potassium, 
KF1,HF1, by heat 

in a platinum retort. This salt breaks up into potassium fluor- 
ide, which remains, and hydrofluoric acid, which is disengaged 
and must be condensed in a platinum receiver cooled to — 20°. 
Pure and anhydrous hydrofluoric acid is liquid at ordinary tem- 
peratures ; it is very mobile, and boils at 19.4° (Gore). It is 
extremely corrosive, and manipulations with it should be con- 
ducted with great care. Its affinity for water is so great that 
each drop of the acid let fall into that liquid produces a hissing 
noise, as would a red-hot iron. The solution is employed for 
etching upon glass, for hydrofluoric acid attacks and corrodes 
that substance. This effect is due to the action of the acid 
upon the silica of the glass, which it converts into either sili- 
con fluoride or hydrofluosilicic acid, as will be seen farther on. 





A design may readily be engTaved on glass by covering the 
glass with a thin coating of wax, through which the design is 

12* 



138 



ELEMENTS OF MODERN CHEMISTRY. 



traced with a sharp point ; the glass is then placed over a leaden 
capsule containing a mixture of powdered calcium fluoride, and 
sulphuric acid (Fig. 51), which is gently heated by a spirit-lamp. 
Hydrofluoric acid vapor is disengaged and attacks the glass 
wherever it is not protected by the wax. When the wax is re- 
moved, the design is found to be permanently etched on the glass. 
A dilute solution of hydrofluoric acid or a bath of hydro- 
fluoride of potassium fluoride may be employed instead of the 
vapor in the former experiment, but in this case the etched 
portions are transparent and not opaque as when produced by 
the vapor ; they may be rendered opaque by adding a salt, such 
as potassium or ammonium sulphate, to the bath. 



NITROGEN. 

Density compared to air 0.9714 

Density compared to hydrogen 14.1 

Atomic weight N =14. 

Nitrogen is one of the elements of the air, and it was from 
air that it was first obtained in a pure state by Lavoisier and 
Scheele, in 1777. To obtain nitrogen from the atmosphere it 
is only necessary to remove the other element, oxygen. 

Preparation. — A flat piece of cork, B (Fig. 52), floating in 
the pneumatic-trough, supports a small capsule containing a 

fragment of phos- 
phorus. The latter 
is inflamed, and the 
capsule immediately 
covered with a bell- 
jar. The heat pro- 
duced by the com- 
bustion at first ex- 
pands the air and 
drives out a portion, 
but in a few minutes 
the water rises in 
the jar, taking the 
place of the oxygen 
which has been con- 
sumed. When the 
phosphorus is extinguished, the experiment has terminated. 
The water gradually dissolves the white smoke of phosphoric 
oxide which fills the jar, and there remains a colorless, irre- 




FiG. 52. 



AMMONIA. 



139 



spirable gas that will not support combustion. This gas is 
nitrogen, still mixed with traces of oxygen and carbonic acid gas. 

Pure nitrogen may be obtained by passing a current of air, 
previously freed from moisture and carbon dioxide, through a 
porcelain tube containing incandescent copper. The copper 
absorbs the oxygen, and pure nitrogen passes out at the end 
of the tube and may be collected over the pneumatic trough. 

Pure nitrogen may also be obtained by heating ammonium 
nitrite in a glass retort ; heat decomposes this salt into nitrogen 
and water. 

(NH*)NO' = 2H'^0 ■+ K' 

Ammonium nitrite. 

Properties. — Nitrogen is a colorless gas, somewhat lighter 
than the air. A litre of this gas weighs 1.257 grammes. It 
extinguishes burning bodies, and is not combustible itself; it 
produces no precipitate in lime-water. Water dissolves only 
■^ of its volume of nitrogen at 0°. Animals are quickly suffo- 
cated in an atmosphere of pure nitrogen, but the gas does not 
exert a poisonous influence upon the economy. 

The affinities of nitrogen are not energetic. It combines 
directly with only a very small number of elements, among 
which may be mentioned carbon, silicon, boron, and titanium. 

Under the influence of a series of electric discharges it will 
unite with oxygen, forming nitrogen peroxide ; with hydrogen, 
forming ammonia. 

AMMONIA. 

Density compared to air 0.596 

Density compared to hydrogen 8.60 

Molecular weight NH^ = 17. 

Ammonia was discovered by Priestley, studied by Scheele, 
and analyzed by Bertholet in 1785. 

Preparation. — Equal weights of quick-lime and sal am- 
moniac, both in powder, are rapidly mixed in a mortar, and 
the mixture introduced into a glass flask, which is then filled 
up with fragments of quick-lime. A cork and delivery-tube 
are adapted to the flask, which is then gently heated and the 
gas disengaged collected over mercury. 

The calcium oxide or lime decomposes the ammonium 
chloride (sal ammoniac), with the formation of calcium 
chloride, ammonia gas, and water; the latter is absorbed by 
the fra2;ments of lime which fill up the flask. 

2NH*C1 + CaO = 2Nff + CaCP -f- H^O 

Ammonium chloride. Calcium oxide. Ammonia. Calcium chloride. 



140 ELEMENTS OF MODERN CHEMISTRY. 

A solution of ammonia in water may be prepared by passing 
the gas through a series of Wolff's bottles, about half filled with 
water, excepting the first, which should only contain a small 
quantity destined to wash the gas. 

Physical Properties. — Ammonia is a colorless gas, having 
a powerful and pungent odor, which excites tears. Its taste is 
burning and caustic. It may be liquefied by a temperature of 
- — 40°, or at 10° under a pressure of 6j atmospheres. Fara- 
day's method of liquefying it is as follows : ammonia is passed 
over dry silver chloride, by which it is absorbed. The silver 
chloride, saturated with ammonia, is introduced into a bent 
tube (Fig. 53), the empty limb of which is then sealed at the 




Fig. 53. Fig.54. 

blow-pipe. The end containing the chloride is now heated in 
a water-bath, while the empty end is cooled in a freezing mix- 
ture (Fig. 54). The ammonia is driven out from th« silver 
chloride, and condenses into a transparent liquid in the cooler 
branch. Faraday succeeded in solidifying ammonia by subject- 
ing this liquid to rapid evaporation. In the solid state it is a 
white, crystalline, transparent substance, fusible at —75°, and 
having only a feeble odor. According to Bunsen, liquid ammo- 
nia boils at — 35° under a pressure of 0.7493 metre : its density 
is 0.76. 

Ammonia gas is very soluble in water, which dissolves 1000 
times its volume at 0°, and about 740 times its volume at 
15°. The rapid absorption of ammonia by water may be strik- 
ingly shown by the following experiment. A bottle, A (Fig. 55), 
is filled with ammonia gas, and fitted with a cork, through 
which passes a tube drawn out at both extremities, and the 
outer end of which is sealed. If this end be plunged under 
water and the point be broken off, the water at once rises into 



AMMONIA. 



141 



the bottle, forming a fountain, and the vessel becomes filled 
with water in a very short time. 

The aqueous solution of ammonia possesses the odor of the 
gas; it is caustic, and 
was formerly called vol- 
atile alkali and spirits 
of hartshorn. It is 
largely used in the arts 
and as a reagent. Its 
density is 0.855. When 
heated, it loses ammonia 
gas, the whole of which 
may be driven out by 
boiling. 

Composition of Am- 
monia.— 200 volumes 
of ammonia gas are in- 
troduced into an eudi- 
ometer, and electric 
sparks are passed 
through the gas for 
some time by means of 
a RuhmkoriF coil (Fig. 
56). When the experiment has terminated, the volume of 
gas will.be found to have doubled. 200 volumes of oxygen 
are added to the 400 volumes of gas thus obtained, and a spark 
is passed; an explosion takes place, and after making the 




Fig. 




necessary corrections for temperature and pressure, the 600 
volumes of gas are found to be reduced to 150 volumes ; 450 
volumes have thus disappeared to form water. 



142 



ELEMENTS OF MODERN CHEJUISTRY. 



These 450 volumes must have contained 

300 volumes of hydrogen, 
150 volumes of oxygen. 

Consequently the 200 volumes of ammonia gas, which were 
decomposed by the spark into 400 volumes, must have been 
formed by the union of 

300 volumes of hydrogen, 
100 volumes of nitrogen. 

The latter gas remains in the eudiometer, together with the 
50 volumes of oxygen that were employed in excess. 

From this analysis it is seen that two volumes of ammonia 
contain three volumes of hydrogen and one volume of nitrogen, 
a composition which is expressed by the formula Nff. 

Chemical Properties. — Ammonia gas is decomposed by a 
high temperature, as by a series of electric sparks. The experi- 
ment may be made by passing the gas through a porcelain tube 




Fig. 57. 

filled with fragments of broken porcelain and heated to white- 
ness, and collecting the gas resulting from the decomposition in 
vessels filled with water (Fig. 57). This gas is found to be a 
mixture of three volumes of hydrogen and one volume of 
nitrogen. 

The decomposition takes place more readily if iron, copper, 
or platinum wires be introduced into the porcelain tube. The 



AMMONIA. 



143 



latter metal is not altered, but the iron and copper become 
brittle and retain a few per cent, of nitrogen. The decompo- 
sition of the ammonia seems here to be favored by the forma- 
tion of metallic nitrides, unstable compounds which are almost 
entirely decomposed by the prolonged action of the heat. 

Ammonia gas will not burn in the air, but a mixture of four 
volumes of ammonia and three volumes of oxygen will explode 
on the application of a flame. 

2NH=' + 0^ = 3W0 + N^ 



Ammonia will burn in an atmosphere of oxygen, 
ammonia escaping 
through a tube drawn 
out to a point may be 
ignited on the instant 
that it is plunged into 
a jar of oxygen, and 
will continue to burn 
with a yellowish flame 
until the oxygen is 
consumed (Fig. 58). 

Independently of 
this rapid combus- 
tion, ammonia may 
undergo a slow com- 
bustion under the fol- 
lowing conditions : 

The vessel A (Fig. 59) contains a solution of 
above which is suspended a spiral of platinum wire. 



A jet of 




ammonia, 
The solu- 



tion is gently heated, and a rapid current of oxygen gas is 
forced through it. The mixed ammonia and oxygen* gases 
come in contact with the platinum spiral and combine together, 
their union developing so much heat that the spiral is heated 
to redness. The vessel sometimes becomes filled with white 
fumes of ammonium nitrite. The nitrous acid is produced by 
the slow oxidation of the ammonia. If a mixture of oxygen 
and ammonia gases be passed through a heated tube contain- 
ing spongy platinum, nitric acid and water will be formed 
and disengaged in vapor. 

Action of Chlorine and Iodine upon Ammonia. — Chlorine 
instantly decomposes ammonia, combining with its hydrogen. 
If a drawn-out tube through which a jet of ammonia is escaping 



144 



ELEMENTS OF MODERN CHEMISTRY. 



be plunged into a bottle filled with dry chlorine (Fig. 60), the 
ammonia takes fire immediately, and white vapors of ammo- 
nium chloride are formed. 

4NH=^ H- CP = 3NH*C1 + N 

If a long tube closed at one end be almost entirely filled 
with saturated chlorine water and then filled up with a solu- 
tion of ammonia, and quickly 
inverted on the pneumatic 
trough, the lighter solution of 
ammonia will rise through the 
chlorine-water and will be de- 
composed according to the pre- 
ceding equation. Ammonium 
chloride will remain in solution, 
while the nitrogen will collect 
at the top of the tube. 

Nitrogen Chloride. — Under 
other conditions the nitrogen 
may combine with the chlorine, 
forming a very explosive and 
dangerous compound, nitrogen 
chloride. 

This experiment may be made 
as follows : A small jar of chlo- 
rine is inverted in a saucer con- 
The ammonia of 
this salt is slowly decomposed by the chlorine, with the for- 
mation of hydrochloric acid and 
nitrogen chloride. 

As the chlorine is absorbed, the 
level of the liquid in the jar rises 
and a drop of a yellow liquid soon 
collects on the surface. A light tap 
on the vessel causes it to sink through 
the solution into the saucer. This 
oily body is nitrogen chloride. The 
jar may now be removed and a small 
piece of phosphorus thrown into the 
saucer, and pushed from a distance 
towards the drop of nitrogen chloride 
by the aid of a . long wooden rod. 




Fig. 59. 
tainine; a solution of ammonium chloride 




Fig. 60. 



AMMONIA. 145 

As soon as the two substances come into contact, the nitrogen 
chloride explodes and the saucer is broken into pieces. 

The formula NOP has been attributed to this body. 

Nitrogen Iodide. — There is another explosive compound 
analogous to nitrogen chloride, but containing iodine. It is 
obtained as a black powder by treating powdered iodine with 
ammonia; when dry it explodes with great violence on the 
lightest touch, and sometimes spontaneously. Bunsen has 
attributed to it the formula N'H^^P. 

According to Stahlschmidt, the composition of nitrogen 
iodide corresponds to the formula NF, when this body is pre 
pared by the action of an alcoholic solution of iodine upon 
aqueous ammonia ; but if both bodies be in alcoholic solution, 
an iodide is obtained having the formula NHP. 

If this be correct, these bodies present very simple relations 
with ammonia. 



N-^ H 


(CI 


N .' I N .' I 
(l (H 


N^Cl 


I CI 


Ammunia. 


Nitrogen cliloride. 


Triiodammonia. Diiodammonia 




Trichlorammonia. 


Nitrogen iodides. 



The substitution of the chlorine or iodine for hydrogen takes 
place atom for atom. 

Action of Potassium upon Ammonia. — When potassium 
is heated in an atmosphere of ammonia, the brilliant surface 
of the metal becomes covered with a greenish-black liquid, 
and at the same time hydrogen is disengaged. The metal 
entirely disappears little by little, and, on cooling, the liquid 
solidifies to an olive-green mass. This substance represents 
ammonia in which one atom of hydrogen has been replaced 
by an atom of potassium. 

H) K) 

H V N = Ammonia. H >■ N = Potassium amide. 

h] HJ 

When it is treated with water, ammonia is regenerated and 
potassium hydrate is formed. 

KNH^ + H^O = KOH + NH' 

Potassium amide. Potassium hydrate. 

Ammonium Amalgam. — If liquid amalgam of potassium 

or sodium and mercury be treated with a saturated solution of 

ammonium chloride, the amalgam increases in volume, assumes 

a buttery consistence, and is converted into a soft, light mas& 

G 13 



146 ELEMENTS OF MODERN CHEMISTRY. 

having the metallic lustre of mercury. It will retain the 
impression of the finger and will float upon water ; but it 
gradually decomposes, losing hydrogen and ammonia, and only 
mercury remains. This unstable body is called ammonium 
amalgam. In it the mercury is combined with a group, NH*, 
which contains all of the hydrogen of the ammonium chloride, 
the chlorine of which has combined with the potassium. 
NHIHCI — CI = NH* 

Ammonium chloride. Kadical ammonium. 

It has recently been found that the ammonium amalgam is 
very compressible, and that its diminution in volume under 
pressure sensibly follows Mariotte's law. It has hence been 
concluded that the ammonium does not exist in combination 
with the mercury, and that the increased volume of the latter 
is due simply to an absorption of gas. It is difficult to admit 
this, for the compressibility of the ammonium amalgam proves 
only that the compound has no stability, and begins to decom- 
pose almost immediately on its formation. The disengaged 
gases, which are in the exact proportion NH^ -[- H, may be 
retained by the pasty amalgam remaining : they could not be 
absorbed by the liquid mercury. 

Ammoniuni Theory. — The reaction which has just been 
described is of great importance, and directly supports the 
ammonium theory suggested by Ampere. According to this 
theory, the ammoniacal salts are analogous in constitution to 
ordinary salts, from which they differ only by the substitution 
of a compound radical, ammonium, for a simple radical. The 
following formulae explain this proposition : 

NH^HCl = (NH*)C1 analogous to KCl 

Ammonium cliloride. Potassium chloride. 

NHIHNO^ = (NH*)N03 analogous to KNO^ 

Ammonium nitrate. Potassium nitrate. 



NHIH^S . --= ^h|s analogous to ^j 

Ammonium sulpliydrate. Potassium si 

(NH^)IH^S =■- ^g! I S analogous to | j S 



Ammonium sulphide. Potassium sulphide. 

AMMONIUM CHLORIDE. 

NH*C1 
This salt was formerly obtained from Egypt, where it was 
made by subliming the soot produced by the combustion of 



AMMONIUM SULPHYDRATE AND AMMONIUM SULPHIDE. 147 

camel's dung. It is now prepared in large quantities from gas- 
liquor, or the water condensed in the manufacture and purifi- 
cation of illuminating gas from coal. This liquor is heated 
with lime, ammonia is disengaged and is conducted into hydro- 
chloric acid. Ammonium chloride is obtained by simply 
evaporating the solution. It, is purified by sublimation in 
stoneware pots which are heated in a furnace out of which the 
upper parts of the pots project. There the volatilized chloride 
condenses, and the sublimed product is known in commerce as 
sal ammoniac, or muriate of ammonia. 

It generally occurs as white or grayish, compact masses, 
having a crystalline fibrous structure. Its taste is sharp and 
salty. It dissolves jn two and a half parts of cold, and in its 
own weight of boiling water. It is deposited from a satu- 
rated solution in small octahedra, grouped together in needles, 
and presenting a fern-leaf-like appearance. At a high tem- 
perature it volatilizes without melting and sublimes without 
decomposition. 

Ammonium chloride is formed by the union of equal vol- 
umes of hydrochloric acid and ammonia gases. 

AMMONIUM SULPHYDRATE AND AMMONIUM 
SULPHIDE. 

Hydrogen sulphide and ammonia gases unite in the cold 
in two different proportions, forming two compounds, ammo- 
nium sulphydrate and ammonium sulphide. 

H^S -f NH^' = ^h}^ 

Hyrogen sulphide. Ammonia. Ammonium sulphydrate. 

(2 vol.) (2 vol.) 

WS + 2NH^ := ^g, 

Hydrogen sulphide. Ammonia. Ammonium sulphide. 

(2 vol.) (4 vol.) 

These compounds are definite, but are decomposed into their 
elements by heat. Horstmann and Salet have shown that hy- 
drogen sulphide and ammonia gases may be mixed in all pro- 
portions without contraction in volume taking place, provided 
the temperature be maintained above 60°. 

Ammonium sulphydrate is generally obtained in solution by 
saturating aqueous ammonia with hydrogen sulphide. This 
solution is colorless, but acquires a yellow color on exposure to 



148 ELEMENTS OF MODERN CHEMISTRY. 

the air. When a quantity of ammonia is added to it equal to 
that which it already contains, ammonium sulphide, (NH^j^S, 
is formed, which corresponds to potassium sulphide, K^S. 

Ammonium sulphide is largely employed in the laboratory 
as a reagent for the detection of certain metals. 

If ammonium sulphide be added to a solution of ferrous 
sulphate, a double decomposition takes place ; ammonium sul- 
phate is formed and remains in solution, while ferrous sulphide 
forms a black precipitate. 

FeSO* + (NH*)^S = FeS + (NH*)^SO* 

Ferrous sulphate. Ferrous sulphide. Ammonium sulphate. 

The salts of zinc, manganese, cobalt, and nickel are likewise 
precipitated as sulphides by ammonium sulphide. 

The salts of aluminium and chromium are precipitated as 
hydrates, hydrogen sulphide being disengaged. 

The preceding salts are not precipitated by hydrogen sul- 
phide (the zinc salts are not precipitated if they be acid), but 
the latter reagent precipitates in the form of sulphides the salts 
of lead, bismuth, copper, cadmium, mercury, silver, antimony, 
tin, gold, and platinum. The sulphides of the latter four 
metals dissolve in an excess of ammonium sulphide. 

The sulphides of arsenic, tin, antimony, gold, and platinum 
all form compounds with ammonium sulphide, in which the 
latter plays the part of a base. 

AMMONIUM NITRATE. 

(NH*)N03 

Ammonium nitrate is prepared by saturating nitric acid 
with ammonia. It crystallizes in large, transparent, fusible 
prisms, which are very soluble in water and produce a notable 
depression of temperature in the act of solution, extending 
even to — 15°. At 300° ammonium nitrate is decomposed 
into nitrogen monoxide and water. It is used for the prepa- 
ration of nitrogen monoxide, much used as an anaesthetic. 

AMMONIUM CARBONATE. 

When dry carbon dioxide and ammonia gases are mixed in 
the proportion of "1 volumes of the first to 4 volumes of the 
second, they condense, forming a white powder, which is am- 



AMMONIUM SULPHATE — HYDROXYLAMINE. 149 

monium carbamate, a compound which was formerly called 
anhydrous carbonate of ammonia. 

CO' + 2NH» = CO<^^H. 

Ammonium carbamate. 

The ammonium carbonate of commerce is generally consid- 
ered as a sesquicarbonate. It contains 2[C0^(NH*)^] -|- CO^ -|- 
2H^0. It is obtained by heating a mixture of equal parts of 
ammonium sulphate and chalk in a subliming apparatus. 
Ammonia and water are disengaged, and the sesquicarbonate 
of ammonium sublimes. 

Recently sublimed ammonium sesquicarbonate is transparent 
and crystalline. It has a strong ammoniacal odor and a sharp 
caustic taste. When exposed to the air it gradually loses 
ammonia and is converted into ammonium acid carbonate. 

Ammoniimi Acid Carbonate. — This salt, which is com- 
monly known as bicarbonate of ammonia, may be obtained by 
passing a current of carbonic acid gas into aqueous ammonia, 
to saturation. The acid salt is deposited in right rhombic 
prisms. The neutral carbonate of ammonium is not known. 
These salts present the following relations to the hypothetical 
carbonic acid : 





(,(. ONH' 


(,0 ONH' 


Carbonic acid. 


Ammonium acid 


Ammonium 


(Hypothetical.) 


carbonate. 


carbonate. 



AMMONIUM SULPHATE. 

(NH*)2S0* 

This salt is obtained in the arts by passing the ammonia 
that is disengaged when gas-liquor is heated with lime into 
dilute sulphuric acid. It crystallizes in right rhombic prisms. 

It is colorless and has a sharp taste. It dissolves in two 
parts of cold, and in its own weight of boiling, water. It is 
insoluble in alcohol. 

HYDKOXYLAMINE. 
NH2(0H) 
This remarkable compound was discovered by Lossen. It 
is formed when ethyl nitrate is reduced by tin and hydrochlo- 
ric acid. It is also a product of the action of dilute nitric acid 
upon tin, and that of hydrochloric acid and tin upon ammo- 
nium nitrate. 

13* 



150 ELEMENTS OF MODERN CHEMISTRY. 

Finally, Lossen has prepared it synthetically by passing a 
current of nitrogen dioxide over tin moistened with hydro- 
chloric acid, which determines a disengagement of hydrogen. 
2N0 + 3H^ = 2[NHX0H)] 

In the first reactions the nitric acid is reduced by the hy- 
drogen resulting from the action of a dilute acid upon tin, and 
which is then, just as it is set free, in what is called the nascent 

HNO^ + 3H2 = 2H^0 -f Nff.OH 

Nitric acid. 

The hydroxylamine thus formed remains in the liquid com- 
bined with an excess of acid. It possesses the properties of an 
energetic base. It forms definite salts with the acids, and can 
be regarded as ammonia, in which the group OH (hydroxyl) 
has been substituted for one atom of hydrogen. 
r H (OH 

N ^ H N .^ H 

(h U 

Ammonia. Hydroxylamine, 

Thus far it has not been isolated ; when a solution of potas- 
sium hydrate is added to a concentrated solution of a salt of 
hydroxylamine, nitrogen is disengaged and ammonia is formed. 
3(NH10H) =:W -{- NH^ + 3H^0 

Lossen has obtained an aqueous solution of hydroxylamine 
by decomposing a dilute solution of hydroxylamine sulphate 
with the exact quantity of baryta-water suflicient to precipitate 
the sulphuric acid. 

Hydroxylamine possesses reducing properties; it precipi- 
tates copper and mercury in the metallic state from solutions 
of their salts. 

OXYGEN COMPOUNDS OF NITROGEN. 

Five compounds of nitrogen and oxygen are known. 

ATOMIC 
COMPOSITION. VOLUMETRIC COMPOSITION. 

Nitrogen monoxide, or nitrous 

oxide N^O 2 vol. N and 1 v. condensed in 2 v. 

Nitrogen dioxide NO 1 vol. N and 1 v. = 2 v. 

Nitrogen trioxide .... N^O^ 2 vol. N and 3 v. condensed in 2 v. 
Nitrogen tetroxide, or nitrogen 

peroxide N^O* 2 vol. N and 4 v. condensed in 2 v. 

Nitrogen pentoxide, or nitric 

anhydride N^O^ 2 vol. N and 5 v. condensed in 2 v. 



NITROGEN MONOXIDE. 



151 



Nitrogen trioxide and nitrogen pentoxide combine with 
water, forming nitrous and nitric acids. 

Nitrogen trioxide. 
Nitrogen pentoxide. 



2HN0' 

Nitrons acid. 

2HN0^ 

Nitric acid. 



NITROGEN MONOXIDE. 

Density compared to air 1.527 

Density compared to hydrogen 22. 

Molecular weight N^O = 44. 

This gas, known also as protoxide of nitrogen, nitrous oxide, 
and laughing-gas, was discovered by Priestley in 17VG. 

Preparation. — It is obtained by gently heating ammonium 
nitrate in a glass retort. The salt melts, and then decomposes 




i^'lG. 01. 

with effervescence into water and nitrogen monoxide, which 
may be collected over water (Fig. 61). 

(NH*)NO=' =- N^O + 2W0 

Properties. — Nitrogen monoxide is colorless and odorless, 
but possesses a sweetish taste. It is not permanent, and may 
be liquefied by strong pressure. It is liquefied on a consider- 
able scale at present, that it may be transported in small bulk 
for the use of dentists. For this purpose it is compressed in 
strong iron reservoirs. 

A remarkable experiment can be performed as follows : A 
quantity of liquid nitrogen monoxide is poured into a test-tube 
fixed by a cork in the neck of a bottle ; a portion of it 
instantly volatilizes, producing intense cold. If now a little 
mercury be poured into the tube, it will sink through the 
liquid monoxide and immediately be solidified. A small piece 



152 



ELEMENTS OF MODERN CHEMISTRY. 



of incandescent charcoal let fall into the tube will float upon 
the surface of the monoxide, and burn with great brilliancy, 

notwithstanding the intense cold 
by which it is surrounded, as evi- 
denced by the freezing of the 
mercury (Fig. 62). 

Water dissolves about its own 
volume of nitrogen monoxide at 
ordinary temperatures. 

A taper which has been extin- 
guished, but still bears a spark 
of fire, is relighted, and burns 
brilliantly when plunged into a 
jar of nitrous oxide (Fig. 63). 
In the same manner, the combustion of sulphur and phos- 
phorus is eflfected with great 
energy in an atmosphere of 
this gas. 

Equal volumes of nitrous 

oxide and hydrogen form a 

mixture which explodes on 

fe\ / ^"%/ ^ the passage of an electric 

spark or on the application 

l\ of flame. 




Fig. 62. 




N^O -f- H^ = H^O + N^ 

2 2 2 2 

volumes, volumes, volumes, volumes. 

Respiration is a slow com- 
bustion and may be sustained 
for a few seconds by nitrogen 
monoxide. Such inhalation 
does not suffocate but it dis- 
turbs the functions of the 
Yjq 63 nervous system, producing 

anaesthesia, and for this pur- 
pose nitrous oxide is now largely employed by surgeons and 
dentists. The insensibility is frequently preceded by a stage 
of intoxication, hence the name laughing-gas^ which was given 
by Davy. 

It must be added that these exhilarating effects have not 
been observed in recent experiments upon perfectly pure nitro- 
gen monoxide. 



NITROGEN DIOXIDE, OR NITRIC OXIDE. 



153 



NITROGEN DIOXIDE, OR NITRIC OXIDE. 

Density compared to air 1.039 

Density compared to hydrogen . . . . . . 15. 

Molecular weight NO =30. 

Preparation. — This gas was discovered in 1772 by Hales ; 
it is prepared by decomposing cold, dilute nitric acid by metallic 
copper. 

^ 3Cu + 8HN0^ = SCuCNO^')^ + 4H^0 + 2N0 

Copper. Nitric acid. Cupric nitrate. 

The copper and water are introduced into a gas-bottle, and 
ordinary nitric acid is added by means of a funnel-tube ; the 
copper is immediately attacked and dissolved, forming cupric 
nitrate (Fig. 64), and at the same time nitric oxide gas is dis- 
engaged. This gas absorbs oxygen from the air and is con- 




Fig. 64. 

verted into red vapors, which are at first apparent in the gas- 
bottle, but as the evolution of nitric oxide continues, the gas 
in the flask gradually becomes colorless, and may then be col- 
lected in jars over water. 

Properties. — Nitric oxide is a colorless gas. It has recently 
been liquefied by Cailletet. It is decomposable by heat, but 
less easily than the monoxide. It is scarcely soluble in water, 
which only takes up a twentieth of its volume. Its most charac- 
teristic property is the energy with which it absorbs half its 
volume of oxygen, passing into the state of nitrogen peroxide 
or red vapors. 

G* 



154 ELEMENTS OF MODERN CHEMISTRY. 

If a jar filled with nitric oxide be opened to the air, the red 
vapors appear at once. 

2N0 + 0' = N"'0* 

Nitric oxide supports the combustion of certain substances. 
Phosphorus burns in it brilliantly, but the gas does not, like 
oxygen and nitrogen monoxide, relight a taper still presenting 
a spark. 

Hydrogen decomposes nitric oxide at a temperature but 
slightly elevated, forming water and nitrogen. 

NO + H^ == N -I- H^O 

The mixture of the two gases in equal volumes takes fire on 
the application of flame. 

If a few drops of carbon disulphide be poured into a jar of 
nitric oxide, the vapor of the volatile liquid is at once diffused 
throughout the gas, and on the approach of a lighted taper a 
brilliant flash of light is produced, the sulphur and carbon being 
burned by the oxygen of the nitric oxide. 

The light produced by this combustion determines at once, 
and like the solar light, the combination of chlorine and hydro- 
gen. 

When a mixture of nitric oxide with an excess of hydrogen 
is passed through a heated tube containing platinum sponge, 
water and ammonia are formed. 

NO + 5H = H^O + NH^' 

Under other circumstances hydroxylamine may be produced. 

A solution of ferrous sulphate absorbs nitric oxide with 
avidity, assuming a dark-brown color ; this is a characteristic 
property, by which nitric oxide may be recognized. 

NITROGEN TRIOXIDE. 

N203 

This compound is formed when a mixture of nitric oxide 
with a large excess of oxygen is subjected to intense cold. It 
is also formed, together with nitric acid, when nitrogen perox- 
ide is treated with a small quantity of cold water. 

2N^0* -I- H^O = 2HN0' -f N^O^ 

Nitrogen peroxide. Nitric acid. 

It is a blue liquid, which boils at a low temperature. 



NITROGEN PEROXIDE. 



155 



NITROGEN PEROXIDE. 

N02 or N^O* 

Preparation. — When well dried lead nitrate is heated to 
redness it is decomposed into lead oxide and nitrogen peroxide, 
which may be condensed in a well-cooled receiver. 



PbCNO^')^ 

Lead uitrate. 



PbO + 

Lead oxide. 



+ N^O^ 



The first portions of nitrogen peroxide that are condensed 
generally retain a trace of moisture, and present a green color ; 
if the receiver be then changed, there collects a yellow liquid 
which solidifies to a crystalline mass at — 10°. 

Properties. — Nitrogen peroxide is a mobile liquid, almost 
colorless at very low temperatures ; at 0° it has a somewhat 
darker color, and at 15° it is orange-brown. It boils at 22°, 
and its vapor is red. Near the point of ebullition its volu- 
metric composition corresponds to the formula N'^0* ; that is, 
two volumes of nitrogen and four volumes of oxygen are con- 
densed into two volumes of N^O*, and occupy the same space 
as two atoms (one molecule) of hydrogen. 

But at a higher temperature this vapor is dissociated ; that 
is, it is gradually decomposed in such a manner as to occupy 
double its primitive volume. The two atoms of nitrogen and 
four atoms of oxygen which constitute two volumes of N'^O* 
at a low temperature, occupy four volumes at about 70°. 



NO^ 


NO^ 



n'o'^ 



N 



0^ 



Red vapors at 2U°. 



Red vapors at 70°. 



The vapor of nitrogen peroxide is very corrosive, and da 



gerous to inhale. 



A small quantity of cold water decomposes nitrogen perox- 
ide into nitrogen trioxide and nitric acid ; a larger quantity of 
water causes the formation of nitrous and nitric acids. 



N^O* 



+ WO == HNO^ + 

Nitrous acid. 



HNO' 

Nitric acid. 



156 ELEMENTS OF MODERN CHEMISTRY. 

When a mixture of nitrogen peroxide and hydrogen is passed 
over heated platinum sponge, water and ammonia are formed. 

Nitryl Chloride and Bromide. — Like nitric oxide, which 
may be called nitrosyl, nitrogen peroxide may play the part of 
a radical. There exists a chloride and also a bromide of nitro- 
gen peroxide or nitryl. 

NO^Cl NO^Br 

Nitryl chloride. Nitryl bromide. 

The latter compound is formed, together with other products, 
when bromine acts upon nitrogen peroxide at a very low tem- 
perature. The chloride of nitryl has recently been obtained 
by the reaction of phosphorus oxychloride upon silver nitrate. 

POCP -I- 3AgN0^ = Ag^PO* + 3(N0^C1) 

Phosphorus Silver nitrate. Silver phosphate. Nitryl chloride, 

oxychloride. 

Nitryl chloride is a light-yellow liquid, boiling at -|-5° and 
solidifying at — 31°. 

In contact with water, it forms nitryl hydrate (nitric acid), 
and hydrochloric acid. 

NO'Cl + H^O = HCl + HNO^ 

In this reaction, the nitric acid is formed at the expense of 
the water, of which one atom of hydrogen is removed by the 
chlorine and replaced by the radical nitryl. Hence nitric acid 
and water may be said to belong to the same type : 

HOH (NO^)OH 

Water. Nitric acid. 

It is seen that in nitric acid the group NO^ replaces one 
atom of hydrogen in water, this group is therefore monatomic. 

But the atom of hydrogen in nitric acid may also be replaced 
by another nitryl group, and the result is an oxide of nitryl, 
the anhydride of nitric acid, or nitrogen pentoxide. The fol- 
lowing formulae will illustrate the relations between these com- 
pounds and water which is their type : 

h|" H 1/ NO' I" 

Water. Nitric acid. Nitrogen pentoxide. 

(Nitryl hydrate ) (Nitryl oxide.) 



NITROGEN PENTOXIDE — NITRIC ACID. 157 

NITROGEN PENTOXIDE. 

(nitric anhydride.) 

N205 

This compound was obtained by H. Sainte-Claire Deville by 
the action of chlorine upon dry silver nitrate heated to between 
58 and 60°. 

2AgN0^ + Cr^ =: N'^0^ + 2AgCl + O 

Silver nitrate. Nitrogen pentoxide. Silver chloride. 

It may also be obtained by passing the vapor of nitryl chlo^ 
ride over silver nitrate heated to 70°. 

AgO.NO"^ + NO^Cl := AgCl + (NO^)^O. 

Silver nitrate. Nitryl chloride. Nitrogen pentoxide. 

Also, as shown by Berthelot, by the action of phosphorus 
pentoxide upon concentrated nitric acid. 

2HN0' — WO = WO^ 

Nitrogen pentoxide is solid and crystallizes in right-rhombic 
prisms. It melts at 29.5°, and boils between 48 and 50°. It 
is very unstable and explodes spontaneously even when it is 
preserved at a low temperature. 

NITRIC ACID. 
HN03 

The atmosphere frequently contains a trace of nitric acid 
vapor or other compounds of nitrogen and oxygen, and small 
quantities of ammonium nitrate and nitrite may be detected in 
rain-water. After passing a current of air for a long time 
through a solution of potassium carbonate, the liquid is found 
to contain potassium nitrate (Cloez). It may be admitted that 
the compounds of nitrogen and oxygen are formed directly by 
the action of electricity upon the elements of the air. 

The nitrates of potassium, sodium, magnesium, and calcium 
are met with in certain soils, often in abundance. They are 
formed wherever nitrogenized organic matters decompose in 
contact with the air and in presence of porous matters and 
alkaline bases. Under these circumstances, the ammonia re- 
sulting from the decomposition is oxidized to nitric acid. 

The experiments of Cloez have shown that the elements of 

14 



158 



ELEMENTS OF MODERN CHEMISTRY. 



the air may unite directly, forming nitrates in the soil, wherever 
alkaline bases and oxidizable matters are present. 

Preparation. — Nitric acid is obtained by decomposing an 
alkaline nitrate with sulphuric acid. In the laboratory, the 
operation may be conducted in a glass retort, the neck of which 
passes, without cork, into a cooled receiver. 98 parts of con- 
centrated sulphuric acid and 85 parts of sodium nitrate are 
employed. On the application of heat, nitric acid is vola- 
tilized, mixed at the commencement of the operation with red 
vapors. The acid condenses in the receiver as a yellow liquid, 
fuming in the air. Sodium acid sulphate remains in the retort. 



Na 



SO^ 



HNO' 



H^SO* + NaNO^ = jj 

Sodium nitrate. Sodium acid sulphate. 

In the arts, the sodium nitrate is decomposed with a less 
concentrated sulphuric acid, the decomposition of the nitric 
acid during the operation being thus avoided. The operation 
is conducted in cast-iron retorts, A (Fig. 65), the lateral tubes 
of which, B, are adapted to stoneware tubes communicating 




Fig. 65. 



with a series of stoneware bottles, D, where the acid con- 
denses. The temperature is elevated towards the close of the 
operation, and sodium neutral sulphate is formed. 

H^SO* -f 2NaN0^ = Na^SO* -f 2HN0^ 



NITRIC ACID. 159 

Properties. — When perfectly pure, nitric acid is colorless, 
but it rapidly becomes yellow under the influence of light, 
undergoing a partial decomposition. When exposed to the 
air, it gives off abundant white fumes. Its density is 1.52 ; it 
solidifies at — 49°, and boils at 86°. 

When its vapor is passed through a red-hot porcelain tube, 
it is decomposed into nitrogen peroxide, oxygen, and water. 

2HN0=^ = H^O + N^O* + 

The mixture of nitric acid with water produces an elevation 
of temperature. The dilute acid, formed by mixing 42.8 parts 
of water and 100 parts of the concentrated acid, is a colorless 
liquid, boiling constantly at 123° ; yet it cannot be considered 
as a definite compound (Roscoe). 

Nitric acid readily gives up a portion of its oxygen to bodies 
having an afiinity for that element. It energetically oxidizes 
sulphur, phosphorus, arsenic, iodine, silicon, carbon, and most 
of the metals. 

If nitric acid be poured upon red-hot charcoal, the combus- 
tion is vividly intensified by the decomposition of the nitric 
acid, and red fumes appear at the same time. 

Copper decomposes nitric acid with an abundant disengage- 
ment of nitric oxide, which is converted into nitrogen peroxide 
by contact with the air. 

Certain metals attack the dilute acid more readily than the 
concentrated ; iron is one of these metals. 

If dilute nitric acid be poured upon clean iron wire, chemi- 
cal action at once takes place, and there is an abundant evolu- 
tion of red vapor ; but if the same wire be plunged into the 
concentrated acid, no action is manifested ; and further, if the 
strong acid be poured off and replaced by dilute acid, the latter 
undergoes no decomposition ; the iron has become passive by 
becoming covered with a thin layer of gas. But if its surface 
be touched with a copper wire, chemical action is at once re- 
established between the iron and the nitric acid. 

The action of tin upon nitric acid is worthy of notice. Tor- 
rents of red vapOr are disengaged, and the metal is converted 
into a white powder, which is stannic acid. In this reaction 
small quantities of ammonia and hydroxylamine are formed at 
the expense of the elements of the nitric acid, and remain 
combined with the excess of acid. 

The conversion of nitric acid into ammonia may be more 



160 ELEMENTS OF MODERN CHEMISTRY. 

complete. If zinc be introduced into very dilute nitric acid, 
the metal dissolves slowly and without disengagement of gas ; 
the liquid is then found to contain zinc nitrate and ammo- 
nium nitrate. The nascent hydrogen set free from a portion 
of the nitric acid by the zinc reduces another portion of the 
acid, forming water and ammonia. 

Zn + 2HN0^ = Zn(NO-')' + H^ 

Zinc. Zinc nitrate. 

2HN0' + 4H^ = 3H^0 + (NH^)NO^ 

Ammonium nitrate. 

Nitrogen dioxide decomposes nitric acid. When a current 
of this gas is passed through nitric acid, the latter becomes 
colored, according to its concentration, brown, yellow, or bluish- 
green. Under these circumstances the acid is reduced, and 
either nitrogen peroxide or nitrous acid is formed and remains 
dissolved in the liquid, the former communicating a brown, 
the second a blue or green color. 

Nitric acid is one of the most important acids ; it is largely 
used as a reagent. It is employed in the manufacture of sul- 
phuric acid, and also to oxidize certain organic matters, such 
as starch and sugar, which it converts into oxalic acid. 

Nitro-hydrochloric Acid. — A mixture of nitric and hydro- 
chloric acids is called nitro-hydrochloric or nitro-muriatic acid, 
or aqua regiae. This liquid dissolves gold and platinum, and 
it owes this property to the chlorine, which is set at liberty by 
the mutual action of the two acids. 

2HC1 -f 2HN0^ = 2H^0 + N^O* + CF 

When the mixture is left to itself it gradually assumes a 
yellow color, undergoing a partial decomposition, as indicated 
by the above formula ; but this decomposition is limited, and 
only complete in the presence of a metal capable of absorbing 
the chlorine. 

But the reaction between hydrochloric and nitric acids gives 
rise to the formation of other products, noticed by Glay-Lussac 
and Baudrimont ; these are ternary compounds of oxygen, ni- 
trogen, and chlorine. One is a red vapor, condensing at — 7° 
to an orano;e-red liquid. Its composition is probably expressed 
by the formula NOCP. 

It may be regarded as nitrogen peroxide in which one atom 
of oxygen is replaced by an equivalent quantity, that is, two 
atoms, of chlorine. 



PHOSPHORUS. 161 

The other is a gas which does not liquefy at very low tem- 
peratures ; it is nitrosyl chloride, NO. CI. By reacting with 
water it forms hydrochloric and nitrous acids. 

NO.Cl + H^O = HCl + NO.OH 

It will be noticed that nitrosyl chloride bears the same rela- 
tion to nitrous acid that nitryl chloride bears to nitric acid. 
The following formulae will illustrate the constitution of these 
bodies : 

NO.C. NO}, NO}, 

Nitrosyl chloride. Nitrous acid. Nitrogen trioxide. 

N0^cl NO^jo Ngjo 

Nitryl chloride. Nitric acid. Nitrogen pentoxide. 



PHOSPHORUS 

Vapor density compared to air 4.32 

Vapor density compared to hydrogen .... 61.1 
Atomic weight P =31. 

Brandt, an alchemist of Hamburg, while attempting to ex- 
tract the philosopher's stone from urine, discovered phosphorus 
in 1669. But urine contains, only a small quantity of phos- 
phates and can yield but traces of phosphorus, so that this 
body only became generally known to chemists after Gahn 
demonstrated its existence in bones, and Scheele discovered the 
process for its extraction. 

The process of the latter chemist is still in use ; it consists 
in treating bone-ash with dilute sulphuric acid, by which means 
the tricalcium phosphate of the bones is converted into mono- 
calcium phosphate, ordinarily called acid phosphate of lime. 

Ca^PO^^ + 2H2SO* = CaH^CPO*)^ + 2CaS0* 

Tricalcium Calcium acid Calcium 

phosphate. phosphate. sulphate. 

The latter phosphate being soluble is separated from the 
calcium sulphate by filtration, and the solution is evaporated 
and mixed with powdered charcoal. The mixture is dried and 
gradually heated to redness in cast-iron vessels. By this means 
the calcium acid phosphate is converted into calcium meta- 
phosphate by the expulsion of two molecules of water. 
CaH*(PO*)^ = 2W0 + Ca(PO^)^ 

Calcium acid phosphate. Calcium metaphosphate. 

14* 



162 



ELEMENTS OF MODERN CHEMISTRY. 



The latter is strongly heated with charcoal in clay retorts 
(Fig. 66), and is decomposed, yielding carbon monoxide and 
phosphorus which distils over, and leaving a residue of calcium 
pyrophosphate. 

-f- 5C = CaT^O^ + SCO + F 

Calcium Carbon 

pyrophosphate. monoxide. 

The phosphorus condenses in the water in the receiver A, 
in which the neck of the retort C is engacred. 



2Ca(P0-^)^ 

Calcium 
nietaphosphate. 




Fig. 66. 

As it is impossible to expel all of the water from the calcium 
acid phosphate, this water is decomposed by the charcoal, hy- 
drogen and carbon monoxide being formed, together with a 
small quantity of phosphoretted hydrogen. 

100 kilogrammes of bone yield between 8 and 9 kilo- 
grammes of phosphorus. The latter is purified by enclosing 
it in a chamois-skin sack, and strongly compressing it under 
water at 50° ; the phosphorus passes through the leather and 
collects under the water. It is moulded into sticks by being 
drawn up into slightly conical glass tubes, which are then 
plunged into cold water. The phosphorus solidifies and is 
easily drawn from the tubes. 

Physical Properties. — Recently-fused phosphorus is trans- 
parent, colorless, or having a pale-yellow tint, flexible, and soft 



PHOSPHORUS. 163 

enougli to be easily scratched by the nail. One-tenth per cent, 
of sulphur renders it hard and brittle. It has a well-marked 
odor, slightly resembling that of garlic. Its density at 10° is 
1.83. It melts at 44° and boils at 290° ; its vapor is colorless 
and has a density of 4.32 compared to air, or 61.1 compared 
to hydrogen. 

If one volume of hydrogen weighs 1, one volume of vapor 
of phosphorus weighs 61.1, and this number should represent 
the weight of one atom of phosphorus ; now it represents the 
weight of two atoms, and the vapor of phosphorus presents 
the singular anomaly that it contains in the same volume 
twice as many atoms as the simple gases, such as hydrogen 
or nitrogen. If one volume of hydrogen contain one atom, 
one volume of phosphorus vapor contains two, and heat cannot 
dissociate these two atoms in such a manner that they may 
occupy two volumes instead of one. The vapor of arsenic 
presents the same anomaly. 



H 


N 



As^ 



1 volume of 1 volume of 1 volume of I volume of 

hydrogen. nitrogen. phosphorus vapor. arsenic vapor. 

Phosphorus volatilizes below its boiling-point and even below 
its melting-point. At ordinary temperatures it emits vapors in 
a vacuum and even in the air. It is luminous in the dark, 
from which property it derives its name, which signifies light- 
bearer. The cause of this phenomenon is still obscure, but is 
generally attributed to the slow oxidation which phosphorus 
undergoes in the air. 

When a stick of transparent phosphorus is kept under water, 
it gradually becomes opaque and covered with a yellowish- white 
pulverulent powder, while the central parts retain their trans- 
parence. This white phosphorus is still pure, but the surface 
of the stick has divided into a multitude of little particles which 
present a crystalline appearance. Some of them become de- 
tached and remain suspended in the water, giving to the latter 
the property of being luminous in the dark. 

Phosphorus is rapidly dissolved by carbon disulphide and is 
deposited in rhombic dodecahedra on the slow evaporation of 
the solution. 

There is an amorphous variety of phosphorus which differs 
so much from ordinary phosphorus that it presents the prop- 



164 ELEMENTS OF MODERN CHEMISTRY. 

erties of an entirely diiFerent substance. It has a dark brown- 
red color, and is not luminous in the dark. It is insoluble in 
carbon disulphide ; it does not melt and take fire like ordi- 
nary phosphorus when heated to 50°. It is amorphous, and 
presents a conchoidal fracture. Its density is 2.14. Ordinary 
phosphorus is one of the most dangerous poisons, but this red 
body exerts no action upon the economy. At 260° amor- 
phous phosphorus melts, is converted into ordinary phospho- 
rus, and presents the properties of the latter substance on 
cooling. 

Amorphous phosphorus results from a physical change 
brought about by the action of light or heat on the ordinary 
variety. If a stick of phosphorus be exposed to direct sun- 
light, its surface assumes a red color ; or if it be maintained 
for a long time at a temperature of 240°, it is entirely con- 
verted into the amorphous variety. 

This transformation is also accomplished by the influence of 
certain chemical agents. If a small stick of ordinary phos- 
phorus be introduced into a test-tube and a very minute por- 
tion of iodine be allowed to fall upon it, the iodine unites with 
the phosphorus with the production of light and heat. A trace 
of phosphorus iodide is formed, and the remainder of the phos- 
phorus is converted into a hard, black mass, which yields a red 
powder ; this is amorphous phosphorus (E. Kopp, Brodie). 

Thus prepared, this body volatilizes like arsenic, without 
melting, and can be distilled without alteration, condensing in 
a black mass, which contains only traces of iodine. 

Chemical Properties. — Ordinary phosphorus possesses a 
strong afl&nity for oxygen. When exposed to the air it slowly 
oxidizes, and the slow combustion, aided by the moisture of the 
air, produces a mixture of phosphorous and phosphoric acids. 
Schonbein has shown that the slow oxidation of phosphorus 
is accompanied by the formation of small quantities of ozone 
and hydrogen dioxide, and he asserts that ammonium nitrite is 
formed at the same time. 

When heated in the air to a temperature of 60°, phosphorus 
takes fire and burns, producing a bright light and white vapors 
of phosphorus pentoxide. In pure oxygen the combustion is 
accomplished with great brilliancy. 

Phosphorus may be burned under warm water by passing a 
current of oxygen through the melted element by means of a 
tube drawn out to a point (Fig. 67); each bubble of oxygen 



HYDROGEN PHOSPHIDE. 



165 



which comes in contact with the phosphorus produces a bright 
flash. 

Phosphorus takes fire spontaneously in an atmosphere of dry 
chlorine, phosphorus pentachloride being produced. 

Uses of Phosphorus. — This body is principally employed in 
the manufacture of matches. The inflammable tips of friction- 
matches contain either ordinary or amorphous phosphorus. In 
the first case, the phosphorus is mixed with inert substances, 
such as sand or ochre, held together by strong glue ; in the 




Fig. 67, 

second case, the ignition of the amorphous phosphorus, which 
is but slightly combustible, is determined by potassium chlorate, 
to which is also added antimony sulphide. All of these sub- 
stances are made into a paste, into which the ends of the 
matches are dipped. Sometimes the match-sticks are tipped 
with a paste composed of potassium chlorate and antimony 
sulphide, a mixture which only takes fire by friction upon a 
prepared surface, composed generally of amorphous phosphorus 
and antimony sulphide. All of these mixtures are held to- 
gether by strong glue. 

HYDROGEN PHOSPHIDE. 

Density compared to air 1.134 

Densit}' compared to hydrogen 17. 

Molecular weight PH^ = 34. 

This gas was discovered by Gengembre in 1*783. 

When phosphorus is heated with a solution of caustic potassa, 
there is a gas disengaged, which inflames spontaneously on con- 
tact with the air ; this is hydrogen phosphide. It is formed 
according to the following equation : 

3K0H + 4P + SH^O = BKHTO^ -f PH^ 

Potassium hydrate. Potassium hypophosphite. 



166 



ELEMENTS OF MODERN CHEMISTRY. 



Preparation. — 1. Hydrogen phosphide may be prepared by 
heating phosphorus with a strong solution of potassium hydrate, 
or with thick milk of lime, with which the flask (Fig. 68) 




should be almost entirely filled. The gas is conducted under 
the surface of water, and as each bubble arrives in contact with 
the air it takes fire spontaneously, producing a bright flash and 
a wreath of white smoke, which enlarges as it rises in the air. 

2. The same spontaneously inflammable gas is evolved when 
calcium phosphide is thrown into water (Fig. 69). The phos- 
phide of calcium is prepared by passing vapor of phosphorus 
over fragments of incandescent lime ; it instantly decomposes 
water with formation of calcium hypophosphite and sponta- 
neously inflammable hydrogen phosphide. 

However, when calcium phosphide is treated with hydro- 
chloric acid, hydrogen phosphide is produced, which does not 
take fire without the application of heat (Fig. 70). 

In this case, the gas is formed by double decomposition 
between the hydrochloric acid and the calcium phosphide ; the 
calcium combines with the chlorine, forming calcium chloride, 
and the hydrogen of the acid combines with the phosphorus. 

3. In the same manner, when phosphorous acid is strongly 
heated in a small retort, it evolves a hydrogen phosphide which 
is not spontaneously inflammable. 



4HT0^ 

Phosphorous acid. 



PH^ 



3HT0* 

Phosphoric acid. 



COMPOUNDS OF PHOSPHORUS AND CHLORINE. 



167 



Properties. — The gas thus obtained is colorless, and pos- 
sesses a garlicky odor. It is but slightly soluble in water, but 
is soluble in alcohol and in ether. When it is pure it does not 
take fire in the air at a temperature below 100°, and then 
burns with a very luminous white flame. According to Paul 
Thenard, the spontaneous inflammability of the hydrogen phos- 
phide prepared by the methods first mentioned is due to the 

3 





Fig. 70. 

presence of another phosphide, P'^H* ; this is a very volatile 
liquid, extremely inflammable, and the least trace of its vapor 
in hydrogen phosphide gas communicates to the latter the 
property of spontaneous inflammability. 

Hydrogen phosphide is absorbed by a solution of cupric 
sulphate, with the formation of black phosphide of copper. 

The composition of hydrogen phosphide, PH^, recalls that 
of ammonia, NH^, and the analogy between the two gases is 
further revealed by the property common to both of uniting 
with hydriodic acid. There is a compound of hydrogen phos- 
phide with hydriodic acid, a well-defined, solid body, crystal- 
lizing in brilliant cubes. 

PH3.HI or PH*I phosphonium iodide. 

The existence of a solid phosphide of hydrogen has been 
demonstrated, and the formula P^H attributed to it. 



COMPOUNDS OF PHOSPHORUS AND CHLORINE. 
There are two chlorides of phosphorus : 

Phosphorus trichloride . PCl^ 

Phosphorus pentachloridc PCl^ 



168 ELEMENTS OF MODERN CHEMISTRY. 

There are, besides, 

Phosphorus oxychloride POCP 

Phosphorus sulphochloride PSCP 

PHOSPHOHUS TRICHLORIDE. 
PC13 

When a current of dry chlorine is passed over phosphorus 
heated in a small tubulated retort, a liquid compound of chlo- 
rine and phosphorus is formed and may be condensed in a 
cooled receiver. This is phosphorus trichloride. It is a 
fuming, colorless liquid, having a density of 1.45 and boiling 
at 74°. 

If it be poured into water, it at first sinks to the bottom, 
and then rapidly disappears, evolving white fumes of hydro- 
chloric acid, and forming phosphorous acid, which remains in 
solution. 

PCP H- 3H^0 = WFO' -f 3HC1 

PHOSPHORUS PENTACHLORIDE. 
PC15 

In contact with an excess of chlorine, phosphorus trichloride 
absorbs two more atoms of that gas, and condenses into a yellow 
crystalline solid, phosphorus pentachloride. 

This body is volatile, and sublimes without fusion when 
heated, even below 100°. When heated under pressure, it 
melts at 148° and boils at a slightly higher temperature. Its 
vapor density, taken at 336° and reduced to 0°, is equal to 
3.656. This density should be double, supposing that the 
molecule PCP occupies two volumes. The anomaly, however, 
is only apparent, for there are good reasons for believing that 
at the temperature 336° the vapor of phosphorus pentachloride 
no longer exists, and that the compound is decomposed or dis- 
sociated into a mixture of phosphorus trichloride and chlorino, 
a mixture which would give four volumes of vapor for one 
molecule of PCP. 



pn]5 __ f PCP = 2 volumes. 



CP = 2 volumes. 



4 volumes. 

Indeed, when the vapor density of phosphorus pentachloride 
is taken by diffusing it in the vapor of the protochloride, which 



:o 



PHOSPHORUS OXYCHLORIDE. 169 

prevents the dissociation before mentioned, a figure is found 
which corresponds very nearly with the theoretic density 7.21 
(A. Wurtz). 

Phosphorus pentachloride decomposes water with energy, 
forming hydrochloric and phosphoric acids. 

PCP -{- 4:W0 = ffPO* + 5HC1 

When only a small quantity of water is present, hydrochloric 
acid is disengaged, by the exchange of two atoms of chlorine 
for one atom of oxygen, and a colorless liquid is formed which 
is called phosphorus oxychloride. When heated in a current 
of hydrogen sulphide, phosphorus pentachloride is converted 
into the sulphochloride, a colorless liquid boiling at 126^ 

PCP H- WO = 2HC1 + POCP 
PCP + H^S = 2HC1 + PSCP 



PHOSPHOHUS OXYCHLORIDE. 

POCP 

This body is readily obtained by exposing phosphorus penta- 
chloride to moist air until it becomes liquid, and subsequently 
distilling the liquid (A. Wurtz j. It is formed in a great num- 
ber of reactions when phosphorus pentachloride is heated with 
hydrated acids, such as oxalic acid, boric acid, etc., or with 
oxides, such as phosphoric oxide. In these cases, one atom of 
oxygen from the oxidized body is exchanged for two atoms of 
chlorine from the pentachloride (Gerhardt). 

Phosphorus oxychloride is a colorless liquid, boiling at 110°. 
When poured into water, it sinks and is at once decomposed, 
hydrochloric and phosphoric acids being formed. 

POCP + h'}^'= H^}^^' + '^^^1 

Phosphorus oxychloride. 3 molecules water. Phosphoric acid. 

COMPOUNDS OF PHOSPHORUS WITH BROMIXE 
AND IODINE. 

Two bromides of phosphorus are known : 
Phosphorus tribromide, PBr'', a colorless liquid. 
Phosphorus pentabromide, PBr^, a yellow, crystalline mass. 
To the trichloride and tribromide of phosphorus there cor- 
responds a triiodide, concerning which but little is known. 
H 15 



170 ELEMENTS OF MODERN CHEMISTRY. 

The best defined and most important combination of phos- 
phorus with iodine is the compound P'-P. 

Phosphorus Iodide, P^I*. — This body is obtained by dis- 
solving 26 parts of dry phosphorus in 30 or 40 times its weight 
of carbon disulphide, and gradually adding to the solution 203.4 
parts of iodine. The liquor, at first reddish-yellow, becomes 
orange-yellow ; it is distilled on the water-bath to drive out a 
part of the carbon disulphide, and on cooling it deposits a 
bright-red, crystalline mass. This is the iodide P^P. 

It crystallizes in long, brilliant, flattened needles, which are 
flexible, and melt at 100°. On contact with water it is decom- 
posed, forming phosphorous and hydriodic acids, and at the 
same time depositing a yellow, flocculent precipitate rich in 
phosphorus (Corenwinder). 



COMPOUNDS OF PHOSPHORUS AND OXYGEN. 

Phosphorus combines with oxygen, forming two oxides : 

Phosphorus trioxide, or phosphorous oxide . . P^O^ 
Phosphorus pentoxide, or phosphoric oxide . . P^QS 

Each of these oxides can combine with three molecules of 
water, phosphorous and phosphoric acids being thus formed. 

FO^ + 3H^0 = 2HT0^ 
PO^-f 3H^O:=2HTO* 

Besides these two acids there is another containing less oxy- 
gen ; it is hypophosphorous acid, whose corresponding oxide is 
unknown. These three acids form a series containing for three 
atoms of hydrogen and one atom of phosphorus regularly-in- 
creasing quantities of. oxygen ; they may be said to constitute 
diff'erent degrees of oxidation of hydrogen phosphide. 

PH^ hydrogen phosphide. 
PH'^0 (missing). 
PH^O^ hypophosphorous acid. 
PH^O^ phosphorous acid. 
PH'^0* phosphoric acid. 



Constitution of the Oxygen Acids of Phosphorus. — Phos- 
phorous and phosphoric acids are related, — the first to phos- 
phorus trichloride, the second to phosphorus oxychloride. In 



HYPOPHOSPHOROUS ACID. 171 

fact, they are derived from these compounds by the action of 
water. 

P'^'CP phosphorus trichloride. 
P(OH)^ phosphorous acid (phosphorus trihydrate). 
(PO)'"CP phosphorus oxychloride (phosphoryl trichloride). 
(PO)'"(OH)^ phosphoric acid (phosphoryl trihydrate). 

To phosphorus pentachloride, PCP, would correspond a pen- 
tahydrate, P(OH)^, which is unknown. Phosphoric acid would 
be derived from the latter by the loss of a molecule of water. 

P(OH)^ = WO + (PO)(OH)« 

It is seen that in phosphorous acid, as in the trichloride, phos- 
phorus is regarded as playing the part of a triatomic element, 
while it is pentatomic in the pentachloride. 

In hypophosphorous acid, it must be admitted that one atom 
of hydrogen is united directly to the triatomic phosphorus, and 
its constitution is expressed by the formula 

H 

F" -l OH 
OH 

HYPOPHOSPHOROUS ACID. 

H3P02 

When phosphorus is boiled with milk of lime or with a con- 
centrated solution of baryta, a soluble hypophosphite is pro- 
duced, and on treating the solution of barium hypophosphite 
with sulphuric acid, a precipitate of barium sulphate and a 
solution of hypophosphorous acid are obtained ; they may be 
separated by filtration. When sufficiently concentrated, the 
liquor leaves a colorless and very acid syrupy residue, which 
constitutes hypophosphorous acid. 

This acid is decomposed at a high temperature, yielding 
phosphoric acid and hydrogen phosphide. It is gifted with 
energetic reducing properties : it instantly decomposes the salts 
of mercury and silver, setting free the metal. An excess of 
hypophosphorous acid added to a solution of cupric sulphate 
precipitates, by the aid of a gentle heat, hydride of copper, 
Cu^H'^, which is decomposed at 100° into copper and hydrogen 
(A. Wurtz). 



172 ELEMENTS OF MODERN CHEMISTRY. 

Hypophosphorous acid contains three atoms of hydrogen, 
only one of which is capable of being replaced by an equiva- 
lent quantity of a metal. The composition of the hypophos- 
phites is consequently expressed by the following general 
formula : 

in which R' represents a monatomic metal, such as potassium, 
capable of replacing hydrogen atom for atom. 

PHOSPHOROUS ACID. 

H3P03 

Preparation. — Phosphorous acid results from the action of 
water upon phosphorus trichloride, as already seen. It may 
be obtained in a state of purity by evaporating the acid liquor 
resulting from this reaction, and heating the syrupy residue 
in a platinum capsule until the odor of hydrogen phosphide 
is perceptible. On cooling, the acid solidifies to a crystalline 
mass. 

Properties. — These crystals absorb moisture when exposed 
to the air, and are resolved into an intensely acid liquid ; they 
melt at a gentle heat, and are decomposed by a high tempera- 
ture into hydrogen phosphide and phosphoric acid. 

Like hypophosphorous acid, phosphorous acid possesses re- 
ducing properties. 

Its boiling aqueous solution reduces the salts of mercury, 
silver, and gold, and this reduction is favored by the presence 
of ammonia. It converts arsenic acid into arsenious acid. 

Chlorine, bromine, and iodine convert it into phosphoric acid 
in presence of water. 

HTO^ + H^O + CP == 2HC1 + HTO* 

Phosphorous acid contains three atoms of hydrogen, two of 
which are replaceable by an equivalent quantity of a metal. 
It is hence called a dibasic acid. 

The composition of the neutral hypophosphites is expressed 
by the general formula 

R'2HP0^ 
in which R' represents a monatomic metal like potassium or 
sodium. 



PHOSPHORIC OXIDE — PHOSPHORIC ACID. 173 



PHOSPHORIC OXIDE, OK PHOSPHORUS 
PENTOXIDE. 

(PHOSPHORIC ANHYDRIDE.) 
P205 

This compound may be obtained by burning phosphorus in 
a large globe filled with dry air. A dense white smoke is pro- 
duced, and condenses upon the walls of the vessel in flakes like 
snow. This body is the anhydride of phosphoric acid. When 
exposed to the air, it absorbs moisture and is converted into 
metaphosphoric acid. 

PQs -j- H^O = 2HP0^ 

When thrown into water it dissolves with a hissing noise, 
such as is produced by a red-hot iron. 

Phosphoric acid volatilizes at a dull-red heat ; it is undecom- 
posable by heat. It yields the oxychloride when distilled with 
phosphorus pentachloride. 

P^O^ + 3PCP = 5P0CP 

It also yields phosphorus oxychloride when distilled with 
dry common salt (Lautemann). 

PHOSPHORIC ACID. 

(ORTHOPHOSPHORIC ACID.) 
H3P0* 

Preparation. — 1. This acid may be prepared by boiling 
phosphorus with nitric acid. On account of the violence of 
the reaction the operation is difficult to regulate, and even 
dangerous when ordinary phosphorus is employed, but it 
succeeds very well with powdered amorphous phosphorus. 
This is heated with tolerably concentrated nitric acid in a 
retort, fitted with a receiver, and, when the whole of the phos- 
phorus has disappeared, a little nitric acid is added to the 
contents of the retort, and the liquid is concentrated in a 
platinum capsule. When the last portions of nitric acid have 
been driven out, a small quantity of water is added, and the 
syrupy liquid is placed in a bell-jar over a dish containing 
concentrated sulphuric acid. At the end of some time, the 

15* 



174 ELEMENTS OF MODERN CHEMISTRY. 

phosphoric acid is deposited in the form of hard, transparent, 
prismatic crystals. 

2. A current of chlorine may be passed through warm water 
under which is a layer of melted phosphorus. Phosphoric 
acid and hydrochloric acid are formed. 

PCP + 4H^0 = HTO* + 5HC1 

As soon as all of the phosphorus has disappeared the solution 
is evaporated, and the hydrochloric acid is driven out by 
heating the residue to 200°. The residue is dissolved in water 
and forms a solution which will deposit the acid in crystals 
when concentrated as indicated above. 

Properties. — When exposed to the air, these crystals attract 
moisture and deliquesce. Their solution is very acid. It does 
not coagulate white of egg, and it produces no cloud in a solu- 
tion of barium chloride, but it forms a white precipitate of 
ammonio-magnesium phosphate in a solution of magnesium 
sulphate on the addition of ammonia. With silver nitrate to 
which ammonia has been added, it gives a yellow precipitate 
of trisilver phosphate, Ag^PO*. Orthophosphoric acid contains 
three atoms of hydrogen, each of which is replaceable by an 
equivalent quantity of metal. 

PYROPHOSPHOmC ACID. 

When orthophosphoric acid is heated for a long time to 
213° it loses water and is converted into a new acid, which is 
called pyrophosphoric. Two molecules of phosphoric acid lose 
one molecule of water, and then unite to form a single mole- 
cule of pyrophosphoric acid. 



JJ4P207 



The residue constitutes an opaque, semi-crystalline mass, 
composed almost entirely of pyrophosphoric acid. 



PO^OH 


/OH 


^OlH 


POvOH 


|0H -- 


= WO + )o 
PO^OH 


PO^OH 


^OH 


^OH 





METAPHOSPHORIC ACID, 1*75 

Its aqueous solution forms a white precipitate of silver 
pyrophosphate in solutions of silver nitrate. 

H*P^O^ + 4AgN0^ = Ag^P^O^ + 4HN0=^ 

When heated with water, pyrophosphoric acid again com- 
bines with one molecule of that liquid, and is converted into 
phosphoric acid by a reaction the inverse of that by which it 
is formed. 

METAPHOSPHORIC ACID. 
HP03 

Preparation. — When phosphoric acid is heated to redness 
in a platinum crucible, a hard, transparent, vitreous mass is 
obtained on cooling ; this is metaphosphoric acid. 

It is formed by the abstraction of one molecule of water 
from phosphoric acid. 

HTO* — H^O == HPO^ 

It may also be obtained directly from calcium acid phos- 
phate, the preparation of which from bone-ash has already been 
described. A slight excess of dilute sulphuric acid is added 
to the concentrated solution of this salt, and the insoluble cal- 
cium sulphate formed is separated by filtration. Since, how- 
ever, the calcium sulphate is not entirely insoluble in water, 
the solution is concentrated, and alcohol added, which com- 
pletely precipitates the sulphate. The liquid is again filtered, 
the alcohol driven off by evaporation, and the residue heated 
to a temperature near redness to remove the excess of sulphuric 
acid. 

On cooling, a vitreous mass of metaphosphoric acid is ob- 
tained. 

An aqueous solution of metaphosphoric acid instantly pro- 
duces a precipitate of silver metaphosphate in a solution of 
silver nitrate. 

HPO^ + AgNO^ = AgPO^ + HNO' 

A few drops of the acid solution added to white of egg sus- 
pended in water produces an abundant white precipitate. 

The same metaphosphoric acid is formed when phosphoric 
oxide is thrown into a large quantity of cold water, or when it 
is allowed to deliquesce in the air. Under these circumstances, 



176 ELEMENTS OP MODERN CHEMISTRY. 

one molecule of phosphoric oxide combines with only one 
molecule of water. 

P05 _[- WO =-- 2HP0^ 

The preceding considerations establish the existence of three 
phosphoric acids, which differ both in composition and proper- 
ties. To these three acids correspond three salts of silver, and 
it will be seen that the latter differ from the acids only by 
containing silver instead of hydrogen, a substitution which 
takes place atom for atom. 

ACIDS. SILVER SALTS. 

H^PO* phosphoric acid (orthophos- Ag^PO^ trisilver phosphate (ortho- 

phoric). phosphate). 

Jj4p207 pyrophosphoric acid. Ag^P'^O^ silver pyrophosphate. 

HPO"^ metaphosphoric acid. AgPO^ silver uietaphosphate. 

It may be added that, independently of the acids and salts 
of which the composition and nomenclature have just been 
considered, others have been described, the most interesting 
of which are related to the metaphosphates, of which they con- 
stitute polymeric modifications. That is, two, three, four, or 
more molecules of metaphosphoric acid are condensed in a 
single molecule, forming more complicated acids. 

COMPOUNDS OF PHOSPHORUS AND SULPHUR. 

When phosphorus is heated with dry sulphur, or when a 
mixture of the two bodies is melted under water, they combine 
with a vivid combustion which is sometimes accompanied by 
dangerous explosions. The action is less violent with amor- 
phous phosphorus. According to the proportions of these 
bodies which are brought into contact, several combinations of 
phosphorus and sulphur may be obtained, among which the 
trisulphide, P^S'^ and the pentasulphide, P'S^, correspond to 
phosphorous and phosphoric oxides. The pentasulphide may 
be obtained in pale yellow crystals. 



AESENKl 

Vapor density compared to air 10.37 

Vapor density compared to hydrogen . . . . 150. 
Atomic weight As =75. 

Arsenic was discovered by A. Schroeder in 1694. 
Natural State and Extraction. — There exists in nature a 



ARSENIC. 



Ill 



common and abundant mineral which contains iron, sulphur, 
and arsenic, and which is called mispickel ; it is a sulphar- 
senide of iron. When it is strongly heated, the arsenic is 
volatilized and a residue of iron sulphide remains. 

FeSAs = FeS + As 

Mispickel. Iron sulphide. 

The operation is conducted on the large scale in earthenware 
cylinders placed horizontally in a furnace. The arsenic sublimes 
into sheet-iron pipes fitted to the open extremity of the cylin- 
ders which extend beyond the furnace. The volatilization of 
the arsenic is facilitated by the addition of a certain quantity 
of metallic iron. 

The arsenic of commerce may be purified by distilling it with 
charcoal in a stoneware retort. 

Properties. — Recently-sublimed arsenic presents the appear- 
ance of a steel-gray, crystalline mass, having a metallic lustre. 
Its crystalline form is an acute rhombohedron. Its density is 
about 5.7. 

Arsenic volatilizes without melting at a temperature below 
dull redness. Its vapor is colorless. When it is heated under 
strong pressure it melts to a transparent liquid. On exposure 
to the air it loses its lustre and assumes a black-gray color ; in 
this case its surface becomes covered with a thin layer of a 
brown-black pulverulent substance, regarded by some chemists 
as a suboxide of arsenic. 

Arsenic oxidizes when it is 
heated in the air or in oxygen. 

If a small quantity of arsenic 
be thrown upon a red-hot coal, 
white vapors are produced, and 
an alliaceous odor is percep- 
tible. 

A fragment of arsenic may 
be strongly heated in the hori- 
zontal branch of a tube con- 
taining oxygen (Fig. Tl) ; the 
metal takes fire and burns with ^^^' ' • 

bluish flame, producing white vapors of arsenious oxide. 

If arsenic be preserved from the air under a layer of water, 
in which it is insoluble, it oxidizes slowly, in such a manner as 
to form a small quantity of arsenious acid, which dissolves in 

H* 




178 ELEMENTS OF MODERN CHEMISTRY. 

the water. This property explains the efficacy of powdered 
arsenic (commercial cobalt) for poisoning flies. 

If powdered arsenic be sprinkled into dry chlorine, each 
particle burns with a bright flash. The combustion indicates 
the energy of the combination. The arsenic unites with the 
chlorine, being converted into the trichloride AsCP. It also 
combines directly with bromine, with iodine, and with sulphur. 



HYDROaEN ARSENIDE, OR ARSENIURETTED 
HYDROaEN. 

Density compared to hydrogen , 39. 

Molecular weight AsH^ =78. 

Preparation.- — This gas may be prepared by the action of 
hydrochloric acid upon zinc arsenide. 

Zn^As^ + 6HC1 = 2AsH=' + 3ZnCP 

Zinc arsenide. Zinc chloride. 

It is a gas which must be handled with great prudence, as it 
is extremely poisonous. 

Properties. — Hydrogen arsenide is colorless ; its odor is 
penetrating and garlicky. At a red heat it is decomposed 
into arsenic and hydrogen. On the application of flame, it 
burns in the air with a bluish light, producing fumes of 
arsenious oxide. If the supply of air be insufficient, arsenic 
is deposited. With one and a half times its volume of oxygen, 
hydrogen arsenide forms an explosive mixture, the products of 
the combination being water and arsenious oxide. 

2AsH3 + 0« == As^O^ + SH^O 

Chlorine decomposes hydrogen arsenide with a production 
of light and the formation of hydrochloric acid. If an excess 
of chlorine be present arsenic trichloride is formed, but if the 
experiment be made in the presence of water, it is arsenious 
oxide which is formed. 

2AsH3 + 6CP + 3ffO = As^O^ + 12HC1 

Water dissolves about one-fifth of its volume of hydrogen 
arsenide. When this gas is agitated with a solution of cupric 
sulphate, it disappears entirely if the gas be pure, and leaves 
a residue of hydrogen should that gas have been present in 
the free state in the mixture (Dumas). 

3CuS0* + 2AsH3 =r: Cu^'As^ -f SH^SO* 

Cupric sulphate. Copper arsenide. 



ARSENIC CHLORIDE. — ARSENIOUS OXIDE. 179 

ARSENIC CHLORIDE. 

AsCP 

Preparation. — 1. A current of dry chlorine may be passed 
over powdered arsenic contained in a retort, tlie neck of which 
is fitted to a cooled receiver. The chloride formed condenses 
as a yellow liquid, containing an excess of chlorine, from which 
it may be freed by distillation over powdered arsenic (Dumas). 

2. A mixture of 40 grammes of arsenious oxide and 400 
grammes of sulphuric acid is gently heated in a tubulated 
retort, and fragments of fused sodium chloride are gradually 
added ; arsenic chloride distils over and condenses in the 
receiver. 
SH'^SO^ + 6NaCl + As^O^ =- 3Na^S0* + 2AsCP + 3H^0 

Sodium chloride. Sodium sulphate. 

Properties. — Arsenic chloride is a colorless, oily, and very 
dense liquid. It boils at 134°. Its density at 0° is 2.05. It 
gives off white fumes in the air, and is very poisonous. 

An excess of water instantly decomposes it into hydrochloric 
acid and arsenious oxide, which, being but slightly soluble, is 
precipitated. 

2AsCP + 3H^0 = As^O^ + 6HC1 

ARSENIOUS OXIDE. 

Preparation. — This dangerous poison is obtained in the 
arts by roasting arseniferous minerals, particularly mispickel. 
Roasting is an operation which consists in heating a mineral 
in contact with air, by which the oxidizable elements present 
are oxidized. When arseniferous minerals are roasted, arsen- 
ious oxide is formed among other products, and volatilizes, and 
is condensed either in wide horizontal chimneys or in a large 
building divided into numerous communicating compartments, 
through which the vapor is led consecutively. It is collected 
in the form of a powder, and is resublimed in cast-iron pots 
surmounted by sheet-iron cylinders, in which it condenses. 

Properties. — Recently-sublimed arsenious oxide occurs as 
vitreous masses ; but it soon loses its transparency and becomes 
milk-white, presenting the appearance of porcelain. When a 
large piece of the opaque oxide is broken, the interior is usually 
found to be still transparent and vitreous. 



180 ELEMENTS OF MODERN CHEMISTRY. 

Arsenious oxide then exists in two forms : the vitreous 
variety is amorphous ; the opaque is crystalline. The former 
variety changes into the latter by a molecular transformation 
which takes place in the midst of the amorphous vitreous mass. 

Arsenious oxide crystallizes in regular octahedra or in tetra- 
hedra ; sometimes, but more rarely, in right-rhombic prisms. 
It is dimorphous. 

It dissolves slowly in cold water, in which it is but slightly 
soluble, and in this respect there is a curious difference between 
the opaque and the vitreous varieties. The latter is three times 
more soluble than the former ; while one part of the vitreous 
oxide dissolves in 25 parts of water at 13°, one part of the 
opaque variety requires 80 parts of water for its solution at the 
same temperature. 

The aqueous solution of arsenious oxide feebly reddens blue 
litmus. It is almost tasteless. It may be regarded as contain- 
ing normal arsenious acid, H^AsO^, corresponding to normal 
phosphorous acid, H^PO^ ; but this hydrate cannot be separated 
from the solution. On evaporation, the oxide As'^0^ is always 
deposited. 

2H^AsO^^ = As^O^ + 3H^0 

The aqueous solution of arsenious oxide, neutralized with 
ammonia, gives a green precipitate with solution of cupric sul- 
phate ; this is copper arsenite, or Scheele's green. With silver 
nitrate it gives a canary-yellow precipitate of silver arsenite. 

Arsenious oxide is more soluble in hydrochloric acid than in 
water. If a slip of clean copper be introduced into this solu- 
tion, it becomes covered with a steel-gray or black coating of 
arsenic. 

Reinsch's test for arsenic consists in boiling the suspected 
substance with dilute hydrochloric acid and bright metallic 
copper. The arsenic is deposited upon the copper, and by 
carefully heating the latter in a small tube the arsenic vola- 
tilizes and is converted into arsenious oxide, which condenses 
in the crystalline form, easily recognizable by aid of a micro- 
scope. 

By the action of zinc the solution ofAs^O'^ in hydrochloric 
acid disengages hydrogen arsenide ; the zinc displaces the hy- 
drogen of the hydrochloric acid, and, by the action of this 
nascent hydrogen upon the arsenious oxide, water and hydro- 
gen arsenide are formed. 

As^O' -f 6H^ = BH^O 4- 2AsH=^ 



ARSENIOUS OXIDE. 



181 



Marsh's Apparatus. — The reducing action of nascent hy- 
drogen upon arsenious oxide is used for the detection of this 
substance by the aid of MarsJis apparatus. 

This consists of an apparatus for the generation of hydrogen 
(Fig. *72) ; it contains pure zinc and dilute sulphuric acid, and the 
hydrogen burns at the 
drawn-out jet with an 
almost colorless flame. 
If, however, a few 
drops of a solution of 
arsenious oxide be in- 
troduced by the fun- 
nel-tube, the character 
of the flame is at once 
it becomes 
and 
diff"uses a white smoke, 
and if a white porce- 
lain surface be de- 
pressed into it, large 
spots of a brownish 
color are produced. 
These are composed 
of arsenic, which is set free in the interior of the flame by 
the decomposition of the hydrogen arsenide by the heat. 



changed 

bluish, elongated 





Fig. 
ratus. 



73 represents a more perfect form of Marsh's appa- 
The hydrogen, mixed with the hydrogen arsenide, first 
IG 



182 ELEMENTS OP MODERN CHEMISTRY. 

traverses a tube, B, filled with cotton, designed to arrest the 
small drops of liquid which may be carried with the gas ; it 
then passes through a narrow tube wrapped with metallic foil 
and heated to redness in a tube-furnace. The hydrogen arsen- 
ide is decomposed into hydrogen and arsenic, and the latter is 
deposited as a brilliant black mirror in the cooler portion of 
the tube. 

Marsh's apparatus permits the detection of the least trace 
of arsenious or arsenic acid in a liquid. It is of great value 
in medico-legal researches, as arsenious oxide is a common and 
dangerous poison. 

ARSENIC ACID 
H3AsO* 

Preparation. — When arsenious oxide is heated with nitric 
acid having a specific gravity of 1.35, red vapors are disen- 
gaged and the oxide is oxidized into arsenic acid, which may 
be obtained as a syrupy liquid by sufficient concentration. 
When left for a long time in a cool place it deposits colorless 
crystals, which constitute a hydrate 2H^AsO* + H"^0 (E. 
Kopp). These crystals are very deliquescent, and dissolve in 
water with the production of cold. They melt at 100°, losing 
their water of crystallization, and there remains a mass com- 
posed of fine needles, which constitute the normal acid 
H^AsO*. 

When heated for some time to a temperature between 140 
and 180°, this acid loses water, and is converted into j^yro- 
arsenic acid^ H*As"^0'^. 

2H^AsO* — H^O =- H*As^O^ 

Between 200 and 206° another quantity of water is driven 
out, and on cooling there remains a pasty, pearly mass, which 
is metarsemc acid, HAsOl 

H^AsO* — H^^O = HAsO' 

It will be noticed that in their modes of formation and in 
their constitution, arsenic, pyro-arsenic and metarsenic acids are 
analogous to the corresponding acids of phosphorus. 

When metarsenic acid is heated to dull redness, it loses all 
of its hydrogen in the form of water, and is converted into 
arsenic oxide, As^O^. 



2HAsO=^ — H^O = As^Qs 



COMPOUNDS OF SULPHUR AND ARSENIC. 183 

At this temperature the oxide melts, and at a bright-red 
heat it is decomposed into arsenious oxide and oxygen. 

As^O^ = As^O^ + 0' 

When exposed to the air it absorbs moisture, but very slowly, 
and even when treated with water it requires a certain time for 
solution. 

Ordinary arsenic acid, which may be called ortharsenic, is 
very soluble in water ; its solution strongly reddens blue litmus 
and possesses a very acid taste. It is reduced by nascent hydro- 
gen, like the solution of arsenious oxide. When neutralized 
with ammonia, it forms a bluish-white precipitate with solution 
of cupric sulphate, and a brick-red precipitate with silver 
nitrate. Hydrogen sulphide produces no immediate precipitate. 

A solution of sulphurous acid reduces arsenic acid to arse- 
nious oxide, and then on the addition of hydrogen sulphide, a 
yellow precipitate of arsenic sulphide, As'^S^, is formed. 

COMPOUNDS OF SULPHUR AND ARSENIC. 

Three sulphides of arsenic are known: 

Arsenic disulphide, or realgar As^S^ 

Arsenic trisulphide, or orpiment As^S^ 

Arsenic pentasulphide As^S^ 

Arsenic Bisulphide, As^S'^ — This body occurs in nature in 
the form of transparent red crystals, which belong to the type 
of the oblique rhombic prism. 

It is obtained as a red mass having a conchoidal fracture by 
melting 75 parts of arsenic with 32 parts of sulphur. It is 
fusible, and may be crystallized by slow cooling. When strongly 
heated in closed vessels, it boils and distils without alteration, 
but when heated in the air, it burns into arsenious and sulphur- 
ous oxides. The alkaline sulphides and ammonium sulphide 
dissolve realgar, leaving a brown powder which has been con- 
sidered as a subsulphide -of arsenic. Boiling solution of potas- 
sium hydrate also dissolves realgar, forming a mixture of 
potassium arsenite and sulpharsenite ; the latter is a soluble 
compound of arsenic trisulphide and potassium sulphide; a 
brown powder remains undissolved. 

Arsenic Trisulphide, or Orpiment, As^Sl — When a solu- 
tion of arsenious oxide is submitted to the action of hydrogen 



184 ELEMENTS OF MODERN CHEMISTRY. 

sulpliide, the liquid assumes a yellow color without the forma- 
tion of any precipitate, but if a drop of hydrochloric acid be 
added, a yellow, flocculent precipitate of arsenic trisulphide is 
formed at once. 

As'^0=^ + 3H^S = As'^' + 3H^0 

The composition of arsenic trisulphide corresponds to that 
of arsenious oxide, and is the same as that of the orpiment 
found in nature. 

It may also be obtained by fusing together arsenic and sul- 
phur in the proper proportions, or even arsenious oxide and 
sulphur ; in the latter case, sulphurous oxide is disengaged, 
and arsenic trisulphide sublimes. Thus prepared, orpiment 
occurs as crystalline masses of a yellow color, bordering upon 
orange, and a pearly aspect. Its density is 3.459. It is fusible 
and volatile. 

Arsenic trisulphide obtained by precipitation is insoluble in 
cold water, and but slightly soluble in boiling water, but it is 
very soluble in ammonia. By continued boiling with water, it 
yields hydrogen sulphide and arsenious acid (de Clermont 
and Frommsl). It is also dissolved by solutions of the alka- 
line sulphides with the formation of sulpharsenites, compounds 
of two sulphides, in which the alkaline sulphide plays the part 
of a base and the arsenic trisulphide the part of an acid. 
Orpiment also dissolves in solutions of the caustic alkalies with 
the formation of an arsenite and a sulpharsenite. 

Arsenic Peiitasulphide, As^Sl — By the prolonged action 
of hydrogen sulphide upon a solution of arsenic acid, a pale- 
yellow precipitate is obtained, which is arsenic pentasulphide. 

2H^AsO^ + SH^S = As^S^ -f SH^O 
It corresponds to arsenic oxide. 

As'^0^ As^S^ 

Arsenic oxide. Arsenic sulphide. 

The alkaline sulphides dissolve it with the formation of 
sulpharsenates. Among the latter there is one having the 
composition K^AsS*, and which corresponds to the arsenate 
K'^AsO*. It is formed by the following reaction : 

As^S^ + 3K2S = 2(K3AsS*) 

The existence of arsenic pentasulphide has recently been 
questioned, the precipitated body seeming to be a mixture of 
trisulphide and sulphur (de Clermont and Frommel). 



ANTIMONY. 185 

ANTIMONY. 

Sb = 122 

Antimony is generally classed with the metals. It indeed 
possesses the lustre of a metal, and it conducts heat and elec- 
tricity; but in a true chemical classification these physical 
properties cannot overbalance the most striking chemical anal- 
ogies. By its affinities, and by the nature and constitution of 
its compounds, antimony must find a place by the side of 
arsenic, which must itself be classed with phosphorus and 
nitrogen. 

Metallurgy of Antimony. — The most common ore of anti- 
mony, which is a sulphide, was known to the ancients. The 
metal is extracted from it by a very simple process. The sul- 
phide is first separated by fusion from the earthy materials, 
called gangue, with which it is associated ; it is then roasted 
or heated in contact with air. The sulphur is in great part 
expelled in the form of sulphurous oxide gas, and the antimony 
is converted into oxide, which still contains some undecom- 
posed sulphide. The whole is then pulverized, and the pow- 
der mixed with pulverized charcoal impregnated with sodium 
hydrate. This mixture is calcined in crucibles, and the anti- 
mony oxide and a portion of the sulphide is reduced by the 
charcoal ; sodium sulphide is also formed, and this dissolves a 
portion of the antimony sulphide, forming a flux which floats 
upon the molten antimony ; after cooling, the latter is found 
at the bottom of the crucible as a button, easy to separate from 
the scoriae. 

By another process the antimony sulphide is fused with 
metallic iron. Iron sulphide and antimony are formed, and 
the latter collects at the bottom by reason of its greater 
density. 

Perfectly pure antimony is prepared in the laboratory by 
reducing antimonous or antimonic oxide by charcoal. 

Properties. — Antimony is a brilliant white metal, having a 
slightly bluish lustre ; it is brittle, and has a laminated frac- 
ture. Its density is 6.715. It melts at about 450°, and 
sensibly vaporizes at a white heat. 

Antimony may be crystallized by allowing large masses of 
the fused metal to cool slowly, and decanting the liquid por- 
tion. Small acute rhombohedra may be obtained in this 
manner. 

16* 



186 ELEMENTS OF MODERN CHEMISTRY. 

When heated in contact with air, antimony is converted 
into antimonous oxide, Sb^O^. 

If a fragment of antimony be introduced into a cavity 
scraped in a piece of charcoal, and the flame of a blow-pipe be 
directed upon it, it melts, becomes red-hot, and gives off white 
fumes. If now the molten globule be allowed to fall, it 
breaks up into a multitude of smaller globules on striking the 
floor, and each particle rebounds into the air as a brilliant 
spark, leaving behind it a train of smoke. 

Powdered antimony projected into dry chlorine unites with 
that element, producing a brilliant combustion. 

HYDROaEN ANTIMONIDE. 

There is a compound of hydrogen and antimony which has 
not yet been obtained in the pure state, but which, according 
to all probability, is the body SbH^. Like its analogue, hy- 
drogen arsenide, it is decomposed by heat ; it can also be pre- 
pared in Marsh's apparatus by the action of nascent hydrogen 
upon a solution containing antimony, and when decomposed 
by heat it forms metallic rings and mirrors, which it is of im- 
portance to distinguish from those formed by arsenic. The 
following differences are sufficient for this purpose : 

The antimony rings are not displaced when heated in a 
current of hydrogen ; the arsenic rings are volatilized, and 
condense in a cooler portion of the tube. 

The spots and rings of antimony are not dissolved by a solu- 
tion of sodium hypochlorite (Labarraque's solution), which at 
once dissolves those of arsenic. 

The antimony spots are readily dissolved by a drop of nitric 
acid, and the liquid leaves on evaporation a white residue, 
which is not colored by the addition of a drop of silver nitrate 
solution. Under the same circumstances, the arsenical spots 
leave a white residue, which assumes a brick-red color when 
moistened with a solution of silver nitrate, owing to the for- 
mation of silver arsenate. 

COMPOUNDS OF ANTIMONY AND CHLOEINE. 

Two chlorides of antimony are known : 

Antimony trichloride SbCl^ 

Antimony pentachloride SbCl^ 

Antimony Trichloride, SbCP. — This compound, formerly 



COMPOUNDS OF OXYGEN AND ANTIMONY. 187 

known as butter of antimony, is formed by the action of hy- 
drocliloric acid upon antimony sulphide. It is generally pre- 
pared in the laboratory from the residue from the preparation 
of hydrogen sulphide. This acid liquid is distilled in a retort 
provided with a receiver, which is changed as soon as the anti- 
mony chloride which distils over begins to crystallize in the 
neck of the retort. 

This chloride is solid, transparent, and colorless. It melts 
at 73.2°, and boils at 230°. It dissolves in water charged 
with hydrochloric acid, forming a colorless solution, but when 
this liquid is diluted with water there is formed an abundant 
white precipitate, long known as powder of Algaroth. It is 
an oxychloride of which the composition does not appear con- 
stant. There is one which contains SbOCl, and which can be 
regarded as antimony trichloride, in which two atoms of chlo- 
rine have been replaced by one atom of oxygen. 

It is formed by a double decomposition, according to the 
following reaction : 

SbCP + H^O = 2HC1 -h SbOCl 

Antimony Pentachloride, SbCP. — This is formed by the 
action of an excess of chlorine upon antimony or upon the 
trichloride. It is a yellow liquid, giving off white fumes in the 
air. It is volatile, but cannot be distilled without undergoing 
a partial decomposition into chlorine and antimony trichloride. 
When exposed to the air, it absorbs moisture and is converted 
into a crystalline mass, which is a hydrate of the pentachloride. 
When treated with a large excess of water, it is decomposed 
with production of heat, and formation of pyrantimonic and 
hydrochloric acids. 

COMPOUNDS OF OXYGEN AND ANTIMONY. 

Two oxides of antimony are known, corresponding to those 
of phosphorus and arsenic : 

Antimonous oxide Sb^O^ 

Antimonic oxide Sb'-^O^ 

Normal antimonic acid, H^SbO*, corresponding to phosphoric 
and arsenic acids, is not known in the free state, but a derivative 
of this acid exists and may be regarded as antimony antimonate. 
Its composition is Sb^O*, and it is derived from antimonic acid 



188 ELEMENTS OF MODERN CHEMISTRY. 

by the substitution of an atom of antimony for three atoms of 
hydrogen. 

IPSbO'^ antimonic acid. 
SbSbO"* antimony antinionato. 

There is a pyrantimonic and also a metantimonic acid, 
analogous to the corresponding pliosphorus acids : 

Il^Sb^O^ pyrantimonic acid. 
HSbO^ metantimonic acid. 

ANTIMONOUS OXIDE. 

This is obtained by oxidizing the metal in the air. The 
operation may be conducted in two crucibles placed one above 
the other, an opening being pierced in the upper one for the 
access of air. They are heated to redness in a furnace, and on 
cooling, the antimony is found to be partially converted into 
brilliant needles that the ancients called silver flowers of anti- 
mony. The crystals are right rhombic prisms, mixed with 
regular octahedra, for antimonous oxide crystallizes in two 
forms, presenting the same character of dimorphism as arsenious 
oxide. The two compounds are hence said to be isodimorphons. 

When solution of sodium hydrate, or better, sodium carbon- 
ate, is poured into solution of antimony trichloride, a white 
precipitate of antimonous hydrate is formed, and, in the latter 
case, carbonic acid gas is disengaged. 

SbCF + 8NaOH =. H='SbO^ + 3NaCl 

Sodium hydrate. Antimonous hydrate. Sodium chloride. 

This hydrate readily parts with a molecule of water, being 
convertetl into another hydrate, IlSbOl 

Il-^SbO^ — IPO ==. HSbO^ 



ANTIMONY ANTIMONATE. 

Sb^O* 

This compound is formed when antimonous oxide is heated 
for a long time in the air, oxygen being absorbed, or when 
antimonic oxide is strongly calcined, oxygen being then disen- 
gaged. 

It is a white, infusible powder, undecomposable by heat and 
insoluble in water. 



ANTIMONIC OXIDE AND AClDS. 189 



ANTIMONIC OXIDE AND ACIDS. 

When powdered antimony is heated with concentrated nitric 
acid, a white powder is obtained, whicli is metantinionic acid. 
It contains one atom of hydrogen capable of being replaced by 
an equivalent quantity of metal, and thus corresponds to meta- 
phosphoric acid. 

IIPO^ HSbO^ KSbO^ 

Metapliosphoric acid. Metantinionic acid. Potassium inotantinionato. 

When it is heated to dull redness, it loses water and is con- 
verted into antimonic oxide. 

2HSbO^ — H^O = Sb^O*^ 

If antimony pentachloride be poured into an excess of 
water, a white precipitate of pyrantimonic acid is formed. 
It is the analogue of pyrophosphoric acid, and, like the latter, 
contains four atoms of hydrogen. 

IPPO^ H*Sb^O^ K^Sl/0' 

Pyrophosphoric acid. Pyrantimonic acid. Potassium pyrantimonate. 

According to Fremy, potassium pyrantimonate may be 
obtained by heating metantimonic acid or potassium metanti- 
monate with potassium hydrate, in a silver crucible. 

2KSbO' -I- 2K0n = K^Sb^O^ + IPO 

Potassium Potassium Potassium 

metantimonate. hydrate. pyrantimonate. 

The metantimonate may be extracted by water, in which it 
is soluble, from the white mass, called by the ancients dia- 
phoretic antimony, which is obtained by deflagrating in a red- 
hot crucible a mixture of 2 parts of nitre (potassium nitrate) 
and 1 part of powdered antimony. Cold water first dissolves 
potassium nitrate from this mass, and then potassium metanti- 
monate. The solution of the latter salt produces with hydro- 
chloric acid a white precipitate of metantimonic acid. 

SULPHIDES OF ANTIMONY. 

Two sulphides of antimony are known : 

Antimony triKulphide, or fintimonous sulphide . . Sb^S^ 
Antimony pentasulphidc, or antimonic .sulphide . . SVj^S^ 

Antimonous Sulphide, Sb'^Sl — This compound, ordinarily 
called sulphide of antimony, occurs both in the crystalline 



190 ELEMENTS OF MODERN CHEMISTRY. 

form and amorphous. Crystallized, it exists in nature and is 
the mineral commonly known as stibium. It is separated from 
its gangue by fusion, and is thus obtained in gray masses com- 
posed of brilliant needles having a metallic lustre. 

Amorphous, it constitutes the orange-colored precipitate 
formed by the action of hydrogen sulphide upon a solution of 
antimony chloride. This precipitate is insoluble in ammonia, 
but dissolves in ammonium sulphide and in the alkaline sul- 
phides. 

Antimony trisulphide is reduced by hydrogen at a high 
temperature ; hydrogen sulphide is formed, and metallic anti- 
mony remains. 

When heated in the air, antimony sulphide is oxidized with 
formation of sulphurous oxide and antimonous oxide. The 
incompletely roasted residue melts at a red heat, and on cool- 
ing assumes the form of a brown vitreous mass called glass 
of antimony. It is an impure oxysulphide which appears to 

contain the compound Sb^S^O = ^, ^^ > 0. 

Antimony Pentasulphide, Sb'^S^ — When finely-pulverized 
antimony trisulphide is digested with sulphur and a solution 
of sodium hydrate, or a mixture of sulphur, sodium carbonate, 
and lime, the antimony sulphide gradually dissolves in the 
liquid, combining both with sulphur and with the sodium sul- 
phide formed. The product of the reaction is a sulphantimo- 
nate of sodium, which is deposited in fine crystals from the 
concentrated liquid. 

Sb^S^ 4- SNa^S = 2Na3SbS* 

Sodium sulphide. Sodium sulphantimonate. 

The crystals of this compound contain 9 molecules of water 
of crystallization. It corresponds to the sulpharsenate already 
mentioned, and to trisodium phosphate, Na^PO*. 

It is soluble in water, and on the addition of hydrochloric 
acid to its solution, hydrogen sulphide is disengaged and anti- 
mony pentasulphide is precipitated. 

2Na^SbS* + 6HC1 ==: 6NaCl -f Sb^S^ + 3H^S 



General Considerations upon the Elements of the Nitro- 
gen Group. — Nitrogen, phosphorus, arsenic, and antimony, 
and bismuth might be added, form a group of elements allied 
by the most striking analogies. This is made manifest by the 



BORON. 



191 



atomic composition of their compounds, as will be seen in the 
following synopsis : 

HYDROGEN COMPOUNDS. 

NH^ PH^ AsH^ SbH^ 

Ammonia. Hydrogen phosphide. Hydrogen arsenide. Hj'drogen antimonide. 



NCP 

Nitrogen 
trichloride, 



CHLORINE COMPOUNDS. 

PCP AsCP 

Phosphorus Arsenic 

trichloride. trichloride. 

PCP — SbCP 

Phosphorus pentachloride. Antimony pentachloride. 

OXYGEN COMPOUNDS. 



SbCP 
Antimony 
trichloride. 



N^O' 


p2Q3 


As^O^ 


Sb^O'^ 


Nitrogen trioxide. 


Phosphorous oxide 


. Arsenious oxide 


. Antimouous oxide. 


N^O^ 


p205 


As^O^ 


Sb^O^ 


Ijitrogen pentoxide. 


Phosphoric oxide. 


Arsenic oxide. 


Antimonic oxide. 


_ 


JJ3PQ3 


H^AsO^ 


H^SbO^ 




Phosphorous acid. 


Arsenious acid. 


Autimonous acid. 


HNO' 


__ 





HSbO^ 


Nitrous acid. 






Antimonyl hydrate. 





HTO* 


H^AsO* 







Phosphoric acid. 


Arsenic acid. 







H*FO' 


H*As^O^ 


H^Sb^O^ 


Pyrophosphoric acid. 


Pyro-arsenic acid. 


Pyro-antimonic acid. 


HNO^ 


HPO^ 


HAsO^ 


HSbO^ 


Nitric acid, Metaphosphoric acid. 


Metarsenic acid. 


Metantimonic acid. 



If the analogy between nitrogen and phosphorus were com- 
plete, there should be an orthonitric acid, H^NO* = HNO'^ + 
H^O, corresponding to ordinary or orthophosphoric acid. This 
acid is not known as a definite hydrate, but compounds exist 
which are derived from it. Thus, bismuth subnitrate, BiNO*, 
can be regarded as a salt of orthonitric acid, in which three 
atoms of hydrogen are replaced by one atom of triatomic 
bismuth. 



BORON. 

Bo = 11 
Boron is the radical of boric acid. It exists in the amor- 
phous state and crystallized. It was discovered by Gay-Lussac 
and Thenard in 1808. 



192 ELEMENTS OF MODERN CHEMISTRY. 

Preparation. 1. Amorplious Boron. — Boric oxide is re- 
duced by sodium at a red lieat, and the cooled mass is treated 
with dilute hydrochloric acid. The sodium borate which is 
formed is thus dissolved, and a residue consisting of amorphous 
boron is obtained as a dark powder. 

2Bo^O=* + SNa^ = 2Na^BoO'^ + Bo'^ 

Boric oxide. Sodium. Sodium borate. 

2. Crystallized Boron. — Boric oxide is fused with alumin- 
ium ; a part of this metal reduces the boric oxide and becomes 
oxidized, while another part dissolves the boron set free, and 
again deposits it in the crystalline form on cooling (H. Sainte- 
Ciaire Deville). 

AP + Bo^O^ = APO^ + Bo^ 

Properties. — Amorphous boron is a dark-brown powder, or 
brown bordering upon green. It is infusible. Heated to 300° 
in the air, it burns, being converted into boric oxide. Its 
combustion in pure oxygen is very brilliant. Amorphous 
boron possesses a singular affinity for nitrogen. At a red heat 
it absorbs this gas, forming a nitride of boron, BoN. When 
heated to dull redness in an atmosphere of nitrogen dioxide, it 
burns into a mixture of boric oxide and boron nitride ( Wohler 
and Deville). 

Crystallized boron occurs as square octahedra (Sella). In 
this form it is almost as hard as the diamond, and will scratch 
rubies. The color of the crystals varies from yellow to deep 
garnet-red; sometimes they appear black. Their density is 
2.63. 

Crystallized boron energetically resists oxidation, both when 
it is heated in oxygen and when it is subjected to the action of 
fused potassium nitrate. At a bright-red heat it reacts upon 
potassium acid sulphate, sodium hydrate, and sodium carbonate. 
It burns in chlorine at a red heat. 

BOBON CHLORIDE. 

BoCP 

Preparation. — This body, which was discovered by Bcrzc- 
lius, is prepared by Wohler and Deville by heating perfectly 
dry, amorphous boron in a current of chlorine gas, and passing 
the vapor of boron chloride formed into a receiver surrounded 
by a mixture of ice and salt. 



BORON FLUORIDE. — BORIC ACID. 193 

Properties. — In a state of purity, boron chloride is a color- 
less, mobile, and highly-refractive liquid, boiling at 17°. It 
fumes in the air, and is readily decomposed by water into boric 
and hydrochloric acids. 

BoCP + 3ff = 3HC1 -f Bo(OH/ 

BORON FLUORIDE. 

BoFP 

Density compared to air 2.31 

Density compared to hydrogen 34. 

Preparation. — Boron fluoride was discovered by Glay-Lussac 
and Thenard in 1810. It is prepared by heating in a glass 
retort an intimate mixture of one part of boric oxide and two 
parts of powdered calcium fluoride with twelve parts of sul- 
phuric acid. The gas disengaged is collected over mercury. 

3CaFP + Bo^O^ + 3ffS0* = 3CaS0* + 3H^0 + 2BoFP 

Calcium Boric oxide. Calcium sulphate, 

fluoride. 

Properties. — Boron fluoride is a colorless gas, having a suf- 
focating odor. It produces abundant fumes in the air, and is 
very soluble in water, which dissolves about 800 times its 
volume of this gas. Its aflinity for water is so great that it 
carbonizes paper and analogous organic substances, from which 
it removes the elements of water. 

The solution of boron fluoride in water is accompanied by a 
chemical reaction ; when the aqueous solution of this gas, satu- 
rated at the ordinary temperature, is cooled to 0°, crystals of 
boric acid are deposited, and a very acid liquid is obtained, 
known as hydrofluoboric acid ; its composition is expressed by 
the formula : 

BoFPH r= BoFP.HFl 

BORIC ACID. 
H3Bo03 

Preparation. — Boric acid was discovered by Homberg in 
1702. It is found in the free state in the craters of certain 
volcanoes, and exists in solution in the lagoni of Monte- 
Rotondo, in Tuscany. These are muddy little lakes, through 
which arise the gaseous emanations from the fissures of a vol- 
canic soil. The gases (suffioni) contain sensible traces of boric 
I 17 



194 ELEMENTS OP MODERN CHEMISTRY. 

acid, which is dissolved by the water of the lagoni. On evap- 
oration, this water furnishes the crude boric acid. 

Large quantities of borax (sodium borate) are obtained from 
Borax Lake and from Lake Clear, about two hundred and fifty 
miles north of San Francisco, California. The crude borax is 
extracted from a muddy deposit, which is obtained from the 
bottom of the lakes by dredging. 

In the laboratory, boric acid is prepared by decomposing a 
boiling saturated solution of borax or sodium borate with dilute 
sulphuric acid. The latter is added in small portions until 
the liquid strongly reddens litmus-paper ; the solution is then 
allowed to cool, and the boric acid separates in the crystalline 
form. 

Properties. — Pure boric acid crystallizes in pearly scales, 
somewhat greasy to the touch. It dissolves in 25 parts of 
water at 18°, and is much more soluble in boiling water. The 
solution is feebly acid, and changes blue litmus solution to a 
wine color. Boric acid dissolves in alcohol, and the solution 
burns with a green flame. 

When boric acid is heated in a platinum crucible to a tem- 
perature near redness, it loses all of its water, melts, and solidi- 
fies to a transparent glass on cooling. This is boric oxide. 

2WBoO^ = Bo^O^ + 3H'^0 

At a red heat this body dissolves a great number of solid sub- 
stances, particularly the metallic oxides; it then yields variously 
colored glasses on cooling. 

Boric oxide is not decomposed by charcoal at a red heat, but 
if a current of chlorine be passed over an intimate mixture of 
boric oxide and charcoal, heated to bright redness in a porce- 
lain tube, boron chloride and carbon monoxide are formed 
(Dumas). 

Bo^O^ + 3C + 3CP = 2BoCP + 3C0 



SILICON. 

Si = 28 

Like boron, silicon exists amorphous and in the crystalline 
form. It was discovered by Berzelius in 1825. 

Preparation. 1. Amorphous Silicon. — Well-dried sodium 



SILICON. 195 

fluosilicate is heated with half its weight of metallic sodium : 
sodium fluoride is formed and silicon is set free. 

Na^^FP.SiFl* + 2Na^ = 6Na.Fi + Si 

Sodium fluosilicate. Sodium fluoride. 

On cooling, the mass is exhausted, first with cold, and after- 
wards with hot, water ; a brown powder of amorphous silicon 
remains. 

2. Crystallized Silicon. — Deville and Caron obtained crys- 
tallized silicon by projecting a mixture of 3 parts of potassium 
and silicon double fluoride, 4 parts of zinc, and 1 part of 
sodium into a red-hot crucible. Fluoride of sodium is formed, 
and the silicon set free dissolves in the zinc and separates in 
the crystalline form on cooling; it is isolated from the zinc 
by dissolving the button in hydrochloric acid ; the silicon 
remains in the form of brilliant laminae or needles. These 
crystals are of a dark steel-gray color, and possess a metallic 
lustre ; they are composed of chaplets of regular octahedra. 

Properties. — Amorphous silicon is a brown powder, more 
dense than water, in which it is insoluble, and producing dark 
stains on the fingers. When heated in the air, it takes fire and 
burns with a bright light into silicic oxide, SiO^ 

Crystallized silicon has a density of 2.49. It may be heated 
to redness in oxygen without taking fire, but when it is calcined 
with potassium carbonate the latter is decomposed with a vivid 
emission of light, potassium silicate being formed and carbon 
being set free. Crystallized silicon resists the oxidizing action 
of both potassium nitrate and potassium chlorate, but it dis- 
solves slowly in a boiling solution of potassium hydrate, hydro- 
gen being disengaged and potassium silicate being formed. It 
burns when heated to redness in an atmosphere of chlorine, 
silicon chloride being formed. 

HYDEOaEN SILICIDE. 

Probable formula SiH* 

Preparation.— This compound was discovered by Wohler 
and Buff in 1857. Magnesium silicide* is introduced into a 
two-necked bottle, which is then entirely filled with water that 

* Wbhler prepares this silicide by fusing in a crucible a mixture of 40 
parts of magnesium chloride, 35 parts of silicon and sodium double fluor- 
ide, and 10 parts of sodium chloride, these salts being previously mixed 
with 10 parts of sodium in minute fragments. 



196 ELEMENTS OF MODERN CHEMISTRY. 

has been recently boiled. One of the necks of the bottle is 
fitted with a funnel-tube which passes to the bottom of the 
bottle, while to the other is adapted a delivery-tube leading to 
the pneumatic trough ; this tube also should be completely filled 
with water so that there is not a single bubble of air in the 
whole apparatus. Concentrated hydrochloric acid is then 
introduced by the funnel-tube, and immediately reacts with 
the magnesium silicide, forming magnesium chloride, which 
dissolves, and hydrogen silicide, which is disengaged and must 
be collected in jars filled with recently boiled water. 

Properties. — The gas thus obtained is not pure hydrogen 
silicide ; it contains an excess of hydrogen. It is colorless and 
insoluble in water from which the air has been expelled. 
Water containing air in solution oxidizes it. 

If bubbles of the gas be allowed to escape through the water 
of the trough, each bubble takes fire on coming to the surface, 
burning with a bright light and a little explosion, and producing 
a white smoke of silicic oxide. This smoke forms rings like 
those produced by hydrogen phosphide under the same circum- 
stances, but often colored brown by a portion of silicon set free. 

The incomplete combustion of hydrogen silicide is accompa- 
nied by a brown deposit of amorphous silicon. At a red heat, 
hydrogen silicide is decomposed into hydrogen and silicon. 

SILICON CHLORIDE. 

SiCl* 

This compound is formed when silicon is heated to dull 
redness in a current of chlorine, or when a current of the 
latter gas is passed over an incandescent mixture of charcoal 
and silica. 

SiO^ + C^ -L- CI* = SiCl* 4- 2C0 

Silicic oxide. Carbon monoxide. 

Preparation. — Precipitated silica, lamp-black, and oil are 
intimately mixed into a stiff paste. This paste is made into 
little balls, which are put into a crucible, the cover of which is 
then luted on, and the whole is heated to redness in a furnace. 
When cool, the balls are introduced into a porcelain tube or a 
clay retort (Fig. 74), which is then heated to bright redness, 
while a current of carefully-dried chlorine is passed through. 
The silicon chloride and the carbon monoxide formed are 



SILICON FLUORIDE. 



197 



passed througli two U tubes surrounded by a mixture of ice 
and salt. The silicon chloride is thus condensed. 

Properties. — Silicon chloride is a volatile, colorless liquid, 
of an irritating odor. It fumes in the air. Its density is 1.52, 
and it boils at 59°. 

It is instantly decomposed by water, silicic and hydrochloric 
acids being formed. A part of the silicic acid is precipitated 

n 




Fig. 74. 

in the form of a jelly, while another part remains in solution. 

The latter is perhaps a hydrate corresponding to the chloride. 

SiCl* + 4H^0 = 4HC1 + Si(OH)* 

There exists a tetrabromide of silicon, SiBr*, and a tetra- 
iodide, SiP, both corresponding to the chloride which has just 
been described. 

Friedel has recently discovered an iodide, Si^F, remarkable 
as belonging to an entirely new series. 



SILICOJN FLUOEIDE. 

Sin* 

Density compared to air 3.6 

Density compared to hydrogen 52. 

Preparation. — An intimate mixture of silicious sand and 

17* 



198 



ELEMENTS OF MODERN CHEMISTRY. 



finely-powdered calcium fluoride, or fluor spar, is introduced 
into a glass flask (Fig. 75), and a sufficient quantity of sul- 
phuric acid is added to reduce the whole to a creamy consistence. 
A gentle heat is applied, and the gas disengaged may be col- 
lected over mercury. 

2CaFP + 2H^S0* + SiO^ = 2CaS0* -f SiFl* 4- 2H^0 

Calcium fluoride. Silicic oxide. Calcium sulphate. 




Fig. 75. 
Properties.— Silicon fluoride is a colorless, sufibcating gas, 
producing white fumes when allowed to escape into the air. It 
may be liquefied by a low temperature and a strong pressure. 
On contact with water it is decomposed, silicic hydrate separat- 
ing in gelatinous flakes, and hydrofluosilicic acid being formed. 
SSiFl* + SH^O = 2(H'^FP.SiF10 -f H'^SiO^ 

Ilydrofiuosilicic acid. 

Hydrofluosilicic Acid. — A saturated, aqueous solution of 
this acid is a highly acid liquid, fuming in the air, and evapo- 
rating slowly at 40° from a platinum-dish without leaving any 
residue. 

It is prepared by passing gaseous silicon fluoride into water 
under which is a layer of mercury. The delivery-tube must 
dip beneath the surface of the mercury, so that the silicon flu- 
oride can only come in contact with "the water after passing 
through the metal ; otherwise the delivery-tube would become 
obstructed by the deposit of gelatinous silica. 

Hydrofluosilicic acid is employed as a reagent in the labora- 
tory. It precipitates the salts of potassium and sodium, form- 
ing insoluble fluosilicates, K'FP.SiFP. 



SILICIC OXIDE AND ACIDS. 199 

SILICIC OXIDE AND ACIDS. 

(silica.) 

Native State. — Silicic oxide is widely diffused in nature. 
It occurs crystallized, as the different varieties of quartz ; amor- 
phous, as agate, chalcedony, cornelian, flint, etc. ; granulated, it 
is found in sandstones and the sand produced by their disaggre- 
gation ; in this case it is often mixed with variable quantities 
of alumina and oxide of iron. 

Rock-crystal is pure silicic oxide. It occurs as six-sided 
prisms, terminated by pyramids of six faces (Fig. 76). 

As hydrate, silica exists in various minerals, such 
as opal and hydrophane. It is also found in the 
form of pulverulent deposits and in solution in 
many running waters, in large proportion in the 
hot waters of the geysers in Iceland. 

Properties. — Quartz is infusible at the highest 
furnace heats, but undergoes a viscous fusion when 
introduced into the flame of the oxy hydrogen blow- 
pipe. Neither carbon nor potassium is capable of 
reducing it, even at the highest temperatures. It 
is not attacked by acids, with the exception of hydrofluoric 
acid. Boiling alkaline solutions scarcely affect it, but the amor- 
phous varieties of silica, such as flint, as well as opal and the 
other hydrates, dissolve more readily in boiling solutions of the 
alkaline hydrates. 

All of the varieties of silica, when heated to redness with 
the alkalies or alkaline carbonates, combine with the bases, 
forming silicates which enter into fusion at a high temperature 
and solidify to a vitreous mass on cooling. Potassium silicate, 
or soluble glass^ is a transparent mass, soluble in water. When 
hydrochloric acid is added to this solution, potassium chloride 
is formed and silicic acid is precipitated as a gelatinous mass, 
which is not insoluble in water. An aqueous solution of silicic 
acid may be obtained. 

If hydrochloric acid be added to a dilute solution of potas- 
sium silicate, the liquid remains transparent although it contains 
silicic acid. It may be poured into a dialyser, composed of a 
piece of parchment-paper stretched over a wooden or glass ring, 
and floated on the surface of pure water contained in another 
vessel. The potassium chloride gradually passes through the 




200 ELEMENTS OF MODERN CHEMISTRY. 

membrane, as would any crystallizable body, and tlie silicic 
acid remains alone dissolved in the water in tlie dialyser, as 
all other amorphous bodies which are soluble in water would 
do. Graham gave the name dialysis to this separation of crys- 
tallizable bodies, which he named crystalloids^ from uncrystal- 
lizable bodies, which he named colloids^ by means of certain 
membranes. The former bodies pass through the membranes, 
which are, however, impermeable to the colloids. 

The silicic acid which remains in solution probably consti- 
tutes normal silicic acid, H^SiO^ = SiO'^ + 2H'^0. 

This hydrate is not known in the pure state. Ebelmen has 
described a hydrate, H^SiO^, which may be considered as the 
first hydrate of silicic oxide. 

H*SiO* — H^O = H^SiO^ - 
H^SiO* — 2.W0 = SiO' 

There are other silicic hydrates having more complex com- 
positions. 

Uses. — Silica is largely employed in all of its various forms. 
Crystallized quartz, or rock crystal, is used for the manufacture 
of ornaments, spectacle-glasses, and lenses. Chalcedony, onyx, 
and opal are sought for by the lapidary and engraver. Agate, 
which is very hard, is used for the manufacture of mortars, etc. 
Sandstones serve for building purposes and for grindstones; 
sand, for mortars and the manufacture of glass and pottery. 



CARBON". 

C = 12 

Natural State and Varieties. — The carbon of chemists is 
pure charcoal. This substance is known to all ; black, friable, 
light, absolutely fixed, inalterable by the air at ordinary tem- 
peratures, but combustible when heated in the air, it results 
from the calcination of organic matters, and particularly wood, 
in closed vessels. But carbon by no means always reveals 
these same properties. It occurs in nature under forms so 
different that it is impossible to apply a general description to 
all of its known varieties. What could be more different, as 
far as physical properties are concerned, from the soot deposited 
by a smoky flame, or the light, porous, and opaque charcoal, 
than the hard, dense, and transparent substance found in nature 



CARBON. 



201 



in the form of diamond ? Nevertheless, these bodies are com- 
posed of one and the same substance, carbon ; ahke, they all 
burn in oxygen at a high temperature, producing carbonic acid 
gas. 

Among the various forms which carbon assumes, and which 
constitute one of the most curious examples of dimorphism, the 
following may be described : 

Diamond. — This is the hardest of all bodies ; it scratches all 
others, and can only be trimmed by grinding with its own dust. 

It is found crystallized in the form of the regular octahe- 
dron and the modifications thereof, among which must be men- 




FiG. 77. 

tioned the polyhedra of twenty-four and forty-eight faces. The 
faces are generally convexly curved (Fig. 77). 

The density of the diamond is between 3.50 and 3.55. It is 
a bad conductor of heat and electricity ; it strongly refracts and 
disperses light. From this latter fact Newton first divined its 
combustible nature, which was proved, in 1694, by the Floren- 
tine academicians of del Cimento, who burned a diamond in the 
focus of a concave mirror. Lavoisier and Davy repeated this 
celebrated experiment. Exposed to the high temperature of 
the voltaic arc between two carbon poles in a vacuum, the dia- 
mond swells up, blackens, and is converted into a substance 
analogous to coke ( Jacquelain). 

Graphite, or Plinnhago. — This is a crystalline variety of 
carbon, which is found in primitive rocks in brilliant steel-gray 
foliated masses. It sometimes occurs in hexagonal laminae. 
It can be scratched with the finger-nail, and leaves a black 
trace when drawn over paper. Its density is 2.2, and it con- 
ducts heat and electricity. It burns only at very high tem- 
peratures; ordinarily, it contains from one to two per cent, of 
foreign matters. 
I* 



202 ELEMENTS OF MODERN CHEMISTRY. 

It has been obtained artificially. Melted iron possesses the 
property of dissolving carbon at a very high temperature, and 
again depositing it on cooling in the form of hexagonal scales 
of graphite. 

Plumbago is used for the manufacture of lead-pencils and 
crucibles, and is called black lead. 

There are other natural varieties of carbon, but they arc 
far from presenting the same degree of purity as diamond or 
graphite. They are: 

Anthracite^ a hard and compact variety of carbon containing 
from 8 to 10 per cent, of earthy matters. 

Bitmninous coal^ a brilliant, black variety, strongly impreg- 
nated with bituminous ttnd earthy matters. It has been pro- 
duced by the slow decomposition of vegetable matters buried 
in the earth in the early geological ages. This origin is indi- 
cated by the impressions of leaves, stems, and fruits, which are 
evident in certain specimens of this coal. It contains only 
from 75 to 88 per cent, of carbon. When it is calcined in 
closed vessels, it disengages combustible gases and products 
which may be condensed in the liquid form and then separate 
into two layers. One is aqueous and ammoniacal, while the 
other is composed of tar. The residue of the distillation of 
bituminous coal is coke. The interior walls of the cast-iron 
vessels in which coal is distilled become covered with a com- 
pact layer of a gray, dense, hard and sonorous carbon, which 
is a good conductor of heat and electricity. This is the carbon 
of gas-retorts^ and is produced by the igneous decomposition 
of hydrocarbons rich in carbon, which are disengaged during 
the calcination of the coal. 

Fat coals are those which burn with a long flame, softening 
in burning; dry coals burn with a short flame which produces 
less heat than the preceding. 

Lignite is a combustible mineral containing less carbon, and 
more impure than bituminous coal; it is found in the lower 
tertiary formations. Natural jety which is employed for the 
manufacture of ornaments, is a variety of lignite. 

Among the artificial carbons, independently of coke, may 
be mentioned wood charcoal, lamp-black, and animal char- 
coal. 

Wood Charcoal. — When wood is calcined in closed vessels 
it leaves a residue which is ordinary charcoal. It is prepared 
on the large scale by two processes, carbonization in stacks, 



CARBON. 



203 



which is carried on in the forests, and distillation in closed 
vessels. Charcoal is amorphous, brittle, and sonorous, a bad 
conductor of heat and electricity. Its density does not exceed 
1.57. The lighter varieties are the more combustible. Its 
combustion leaves a residue of one or two per cent, of cinders, 
formed principally of mineral salts, among which the most 
abundant are the carbonates of calcium and potassium. 




I 



Lamp-hlach is produced by the incomplete combustion of 
organic substances rich in carbon. When rosin or tallow is 
burned, a dense smoke is produced which is composed of par- 



204 ELEMENTS OE MODERN CHEMISTRY. 

tides of carbon that have escaped combustion. In the arts, 
lamp-black is procured by burning rosin in cast-iron pots, C 
(Fig. 78), heated by a fire, F. The vapors given off' are ig- 
nited, and the smoke is conducted into a chamber. A, the walls 
of which are hung with canvas. On this the lamp-black is de- 
posited, and is detached by lowering the cone B, which acts as 
a scraper. Lamp-black is not pure carbon. It contains tarry 
and oily matters, from which it may be freed by calcination in 
a covered crucible. It is used for the manufacture of printing- 
inks. 

Animal charcoal is produced by calcining animal matters, 
such as blood, the debris of skin, horn, bone, etc., in closed 
vessels. Bone-black or ivory-black contains the calcareous 
salts, calcium phosphate and carbonate, which form the base 
of the osseous tissue. The carbon is consequently disseminated 
through a porous mass. These salts may be extracted by 
treating the bone-black with dilute hydrochloric acid, by which 
they are dissolved. The residue, washed with water and dried, 
is known as washed or purified animal charcoal. 

Absorbent Properties of Charcoal. — The amorphous and 
porous varieties of carbon, of which several forms have been 
described, possess the property of absorbing and retaining in 
their pores, gases, liquid and solid bodies. It is to this absorp- 
tive faculty that are due the decolorizing and disinfecting 
properties of charcoal, which are made use of to a large extent 
in the arts. 

If a piece of incandescent charcoal be plunged into mercury 
that it may cool out of contact with the air, and then be intro- 
duced into a small jar filled with ammonia or hydrochloric acid 
over the mercury-trough, the gas is at once absorbed and the 
mercury rises in the jar. 

The following table, by Th. de Saussure, indicates the quan- 
tities of several gases which are absorbed by one volume of 
charcoal : 

1 volume of charcoal absorbs 90 volumes of ammonia. 



85 


<' 


hydrochloric acid. 


65 


'' 


sulphurous oxide. 


55 


" 


hydrogen su]j)hide. 


40 


<( 


nitrogen monoxide. 


35 


<( 


carbon dioxide. 


9.42 


(( 


carbon monoxide. 


9.25 


(( 


oxygen. 


7.50 


•' 


nitrogen. 


1.75 


i( 


hydrogen. 



CARBON. 



205 



Charcoal increases in weight when exposed to the air, for 
it absorbs and condenses the atmospheric moisture. When 
plunged into water charged with a small quantity of hydrogen 
sulphide, it absorbs that gas and removes the odor of the water. 
The disinfecting properties of charcoal are thus easily explained. 
It is well known that charcoal will remove the unpleasant odor 
of corrupted waters, of meats slightly spoiled, and in general 
of organic matters in a state of putrefaction. A layer of char- 
coal between two layers of sand is an excellent filter for the 
clarification of drinking waters. 

The decolorizing properties of charcoal are another mani- 
festation of this general faculty of absorption, which is pos- 
sessed in the highest degree by animal charcoal. If litmus 
solution or red wine be agitated with a sufficient quantity of 
animal charcoal and subsequently filtered, the liquids pass 
throuo-h colorless. 




Pig. 79. 



This property of animal charcoal is largely applied in the 
arts, particularly for decolorizing sugars and syrups. 

Chemical Properties. — Carbon is distinguished by its 
powerful affinity for oxygen, an affinity which is not, however, 

18 



206 ELEMENTS OF MODERN CHEMISTRY. 

exercised except at high temperatures. It only combines with 
oxygen at a red heat, and remains incandescent as long as com- 
bination goes on, the heat produced by the combination being 
sufficient to maintain the incandescence. In pure oxygen it 
burns with a brilliant light. The product of the combustion 
is carbonic acid gas. 

By the aid of heat, carbon decomposes a great number of 
oxygenized compounds, removing and combining with the 
whole or a part of their oxygen. This decomposition takes 
place at comparatively low temperatures when the oxygenized 
body does not strongly retain its oxygen ;- in this case, carbon 
dioxide is formed, and the reduction of cupric oxide by char- 
coal furnishes an example. In the contrary case, the reduction, 
that is, the decomposition of the oxidized body, requires a very 
high temperature ; carbon monoxide is then formed. The re- 
duction of zinc oxide by charcoal is an example. 

If an incandescent charcoal be rapidly plunged under a bell- 
jar filled with water on the pneumatic trough, bubbles of gas 
arise and collect in the jar (Fig. 79 ). They are formed of a 
mixture of hydrogen, carbon monoxide, and a small quantity 
of carbon dioxide. These gases are produced by the decom- 
position of the water by the charcoal, which was red-hot at the 
moment of contact with the liquid. 

C + H^O = ff + CO carbon monoxide. 

Carbon combines directly with sulphur at a high tempera- 
ture, forming carbon disulphide. 



COMPOUNDS OF CARBON AND OXYGEN. 

Two compounds of carbon and oxygen are ,known : 

Carbon monoxide CO 

Carbon dioxide, or carbonic acid gas CO'-' 

The latter body, which has long been known as carbonic 
acid, is the oxide corresponding to the true carbonic acid, 
which would be 

CO^ + H^O = H'^CO^ 

This normal carbonic acid is as yet unknown : it is doubtless 
too unstable to exist in the free state. However, its existence 



CARBON MONOXIDE. 



207 



may be admitted, for a corresponding 
sulphoearbonic acid H^CS^. 



compound is known in 



CARBON MONOXIDE. 



Density compared to air . . . 0.967 

Density compared to hydrogen 14. 

Molecular weight CO . . = 28. 

Preparation. — 1. An intimate mixture of zinc oxide and 
charcoal may be calcined in a clay retort. 

ZnO + C ^ CO H- Zn 
2. A convenient method of preparing carbon monoxide con- 
sists in heating oxalic acid with an excess of sulphuric acid in 
a glass flask. The oxalic acid loses the elements of water, 
which it yields to the sulphuric acid, and breaks up into carbon 
dioxide and carbon monoxide. 

C^H^O* = CO 4- CO^ + WO 

Oxalic acid. Carbon monoxide. Carbon dioxide. 




The mixture of the two gases is passed through a wash-bottle, 
B (Fig. 80), containing a solution of potassium hydrate, by 



208 ELEMENTS OF MODERN CHEMISTRY. 

which the carbon dioxide is absorbed, potassium carbonate being 
formed. Carbon monoxide alone passes through, and may be 
collected over water. 

Properties. — Carbon monoxide is a colorless, odorless gas. 
It is neutral, and does not trouble lime-water, which distin- 
guishes it from carbon dioxide. It extinguishes burning bodies, 
but is combustible itself, burning in the air with a blue flame, 
and forming carbon dioxide. It is not only unfit for respira- 
tion, but is very poisonous. 

Composition. — If two volumes of carbon monoxide be 
mixed with one volume of oxygen in an eudiometer, and a 
spark be passed, complete combustion takes place, and the 
three volumes of the primitive mixture are reduced to two 
volumes of carbon dioxide. This can be verified by passing 
into the eudiometer a solution of potassium hydrate, which will 
completely absorb the new gas. 

It hence follows that two volumes of carbon monoxide con- 
tain the same quantity of carbon as two volumes of carbon 
dioxide. Knowing from other circumstances that two volumes 
of carbon dioxide contain two volumes of oxygen, it follows 
that two volumes of carbon monoxide contain one volume of 
oxygen. Its composition is then expressed by the formula 
CO = 2 volumes. 

Carbon monoxide undergoes dissociation at a very high tem- 
perature. By operating under special conditions, H. Sainte- 
Claire Daville has succeeded in resolving it into carbon and 
oxygen. 

It is almost insoluble in water, but is absorbed by a solution 
of cuprous chloride in hydrochloric acid (Doyere and F. Le 
Blanc). Advantage is taken of this property in volumetric 
analysis to separate carbon monoxide from certain other gases. 

When heated for a long time to 100°, in sealed tubes with 
potassium hydrate, it combines with the alkali, forming potas- 
sium formate (Berthelot). 

CO + KOH r^ KCHO^ 

Potassium hydrate. Potassium formate. 

It is a beautiful synthesis of formic acid, so named because it 
exists in ants. 

Action of Chlorine upon Carbon Monoxide. — Under the 
influence of sunlight, carbon monoxide combines directly with 
chlorine, forming a gas which is known as chloro-carhonic oxide^ 



CARBON DIOXIDE. 209 

or carhonyl chloride. It was formerly called phosgene gas. 
One volume of carbon monoxide combines with one volume of 
chlorine to form one volume of carbonyl chloride, so that the 
density of the latter is equal to the sum of the densities of 
carbon monoxide and chlorine. 

Compared to Hydrogen. Compared to Air. 
Density of carbon monoxide . . 14. 0.967 

Density of chlorine 35.5 2.44 

Density of carbonyl chloride . 49.5 3.407 

At ordinary temperatures, carbonyl chloride is a colorless 
gas, having a suffocating odor that provokes tears. At a low 
temperature, it condenses to a colorless liquid, boiling at 8.2° 
(Emmerling and Lengyel). It is instantly decomposed by water, 
with the formation of carbon dioxide and hydrochloric acid. 



COCP + WO = 2HC1 + CO^ 

Its mode of formation, its composition, and its properties 
indicate its relations to carbon dioxide. 

2 volumes CO absorb 2 volumes of chlorine to form 2 volumes C0.C12 
2 volumes CO absorb 1 volume of oxygen to form 2 volumes CO.O 

It is seen that carbon monoxide plays to a certain extent the 
part of a radical ; it combines directly with oxygen or with 
chlorine to form either oxide or chloride of carbonyl. It 
is seen also that carbonyl chloride represents carbon dioxide in 
which one atom of oxygen is replaced by two atoms of chlorine. 



CAEBON DIOXIDE. 

Density compared to air 1.529 

Density compared to hydrogen 22. 

Molecular weight CO^ ^44. 

This gas was discovered by Black in 1648, and its composi- 
tion was recognized by Lavoisier in 1776. It is one of the 
constituents of the atmosphere, and is the product of a great 
number of reactions which take place on the earth's surface, 
such as the combustion of carbon and organic matters, respira- 
tion, and the phenomena of putrefaction and fermentation. It 
issues from the soil of volcanic countries. 

18* 



210 



ELEMENTS OP MODERN CHEMISTRY. 



Preparation. — Fragments of marble, which is calcium car- 
bonate, are intro- 
~ duced into a two- 

necked bottle fitted 
with a delivery- 
tube and a safetv- 
tube (Fig. 8f). 
The bottle is half- 
filled with water, 
and hydrochloric 
acid is gradually 
added by the fun- 
nel-tube. An ef- 
fervescence imme- 
diately takes place, 
due to the disen- 
gagement of car- 
bon dioxide. 
- CaCP -f H^O 

Calcium chloride. 




Fig. 81. 



CO^ 



CaCO=^ + 2HC1 = 

Calcium carbonate. 

The gas is most conveniently collected by dry downward 
displacement, like chlorine. 

Composition. — 1. If carbon be burned in oxygen, the latter 
is converted into carbon dioxide without changing its volume. 
Hence two volumes of carbon dioxide contain two volumes of 
oxygen. These two volumes of oxygen, which represent two 
atoms, are combined with one atom of carbon, and the compo- 
sition of a molecule of carbon dioxide is hence expressed by 
the formula 

CO^ = 2 volumes. 

2. Dumas and Stas determined the centesimal composition 
of carbon dioxide by burning a known weight of diamond in 
oxygen, and carefully weighing the carbon dioxide produced. 
By subtracting the weight of the diamond burned from that of 
the carbon dioxide, the weight of the oxygen was determined. 
The apparatus employed is represented in Fig. 82. 

The increase in weight of the tubes L, M, N, 0, P indicates 
the quantity of carbon dioxide formed. 

Dumas and Stas thus found that 100 parts of carbon dioxide 
contain 

Carbon 27.27 

Oxygen 72.73 

100.00 



CARBON DIOXIDE. 



211 




212 



ELEMENTS OF MODERN CHEMISTRY. 



a centesimal relation which is expressed more simply by the 
numbers 

Carbon 12 

Oxygen 32 

44 

12 being the weight of one atom of carbon, and 32 the weight 
of two atoms of oxygen. 

Physical Properties. — Carbon dioxide is colorless ; it has a 
feeble, somewhat pungent odor. A litre of this gas at C°, and 
under the pressure of 760 millimetres, weighs 1.966 grammes. 




Fig. 83. 

It is not permanent. Faraday succeeded in liquefying it at 
a temperature of 0°, under a pressure of 36 atmospheres. The 
apparatus which is now used for its liquefaction is represented 
in Fig. 83. It is composed of two reservoirs, A and B, com- 



CARBON DIOXIDE. 



213 



municating by the metallic tube i, furnished with a stop-cock 
at each end. The cylinders are made of heavy cast-iron, and 
are further strengthened by forged iron bands forced over 
their circumference. Each cylinder is movable on a horizon- 
tal axis, h. B is the generator; into it are introduced 1800 
grammes of sodium dicarbonate, and a cylindrical copper tube, 
I), containing 1000 grammes of ordinary sulphuric acid. The 
cylinder is then closed by a strong screw plug, and a few oscil- 
lating movements are given to it in order that the sulphuric 
acid may gradually run out upon the sodium dicarbonate. 
Carbon dioxide is disengaged and is liquefied by its own press- 
ure as it accumulates in the apparatus. By the eJBfect of the 
chemical action the temperature is raised to 30 or 40°, and, 
communication being established between the two cylinders, 
the carbon dioxide distils rapidly into the receiver, the tem- 
perature of which is about 15°. 

The operation is repeated several times, that one or two kilo- 
grammes of the liquid may accumulate in the receiver. A 
tube passes to the bottom of this vessel, and on opening the 
stop-cock which closes the superior extremity of this tube, a 
jet of the liquid is thrown out with 
force ; it is received tangently in a 
metallic box, A, A' (Fig. 84), having 
very thin sides. In this a portion 
of the oxide solidifies by reason of 
the great depression of temperature 
produced by the change of another 
portion into the gaseous state. A 
glittering-white, flaky mass collects 
in the receiver, having the appear- 
ance of snow. This is solid carbon 
dioxide. It is a bad conductor of 
heat and electricity, and can be ex- 
posed to the air for a few minutes 

before it disappears. In reassuming the gaseous form, it pro- 
duces an intense cold. If it be mixed with ether, the mixture, 
which is less porous and a better conductor of heat, can produce 
a lowering of temperature as great as — 90°. By pouring it 
upon mercury, large masses of that metal may be frozen. 

Drion and Loir have recently succeeded in collecting and 
maintaining carbon dioxide in the liquid state. It is colorless 
and mobile; has a density of 0.72 at -j-27°, and 0.98 at — 8°. 




Fig. 84. 



214 



ELEMENTS OF MODERN CHEMISTRY. 



This considerable difference between the densities is due to tlie 
enormous dilatation which the liquid undergoes between these 
limits of temperature. Indeed, ten volumes of liquid carbon 
dioxide at 0° occupy fourteen volumes at 30°. The coefficient 
of dilatation of the liquid is then superior to that of the gas. 
Carbon dioxide is incombustible, and extinguishes burning 
bodies. 

If carbon dioxide be poured from one vessel into another 
containing a lighted candle, it falls upon the flame like water, 

extinguishing it at once (Fig. 85). 

Lime-water poured into a jar 

.^.^ ^ -^ ofcarbon dioxide becomes clouded, 

^lir "'^'^ \ ^^^ calcium carbonate. 

These experiments permit the 
easy recognition of carbon dioxide 
from carbon monoxide. 

Carbon dioxide dissolves in its 
own volume of water at 15° under 
the normal pressure. If the press- 
ure be increased, the solubility of 
the gas is increased in the same 
proportion. Thus, under a press- 
ure of ten atmospheres one litre 
of water will dissolve ten litres of 
carbon dioxide ; but it must be remembered that under a press- 
ure of ten atmospheres these ten litres are reduced to one litre. 
Thus, one litre of water, which dissolves one litre of carbon 
dioxide at the ordinary pressure, dissolves also one litre under 
a pressure of ten atmospheres, and it may be said that water 
always dissolves its own volume of carbon dioxide, whatever 
may be the pressure. Water saturated with carbon dioxide 
under strong pressure, disengages a portion of the gas as soon 
as the pressure is removed. Such water is universally known 
and consumed in large quantities under the name of gaseous 
water or soda water. 

The solution of carbon dioxide exercises a much more ener- 
getic solvent action upon certain substances than pure water. 
It dissolves calcium carbonate, forming a soluble dicarbonate ; 
it is even capable of dissolving calcium phosphate, transform- 
ing it into acid phosphate, which is soluble. 

Carbon dioxide is more soluble in alcohol than in water. 




Pig. 85. 



CARBON BISULPHIDE. 215 

It is undecomposable by heat alone, but may be decomposed 
or reduced at high temperatures by contact with bodies avid 
of oxygen. Such substances are hydrogen and carbon. With 
the latter body the reduction takes place at a red heat, giving 
rise to the formation of carbon monoxide, the volume of which 
is double that of the carbon dioxide employed. 

CO^ + C == 2C0 

Carbon dioxide (2 vols.). Carbon monoxide (4 vols.). 

CAEBON DISULPHIDE. 

This body is prepared by passing sulphur vapor over incan- 
descent charcoal. In the arts, the operation is conducted in 
cylindrical, cast-iron vessels, filled with charcoal and heated to 
redness, into which sulphur is introduced. The carbon disul- 
phide distils, and is condensed in a suitable cooling apparatus. 

Carbon disulphide is a colorless, very mobile, and highly-re- 
fracting liquid. Its odor is strong and unpleasant. Its density 
at 15° is 1.271, and it boils at 46°. It is very inflammable, and 
burns with a blue flame, producing sulphurous oxide and carbon 
dioxide. 

CS^ + 0« = 2S0' + CO^ 

Its vapor, mixed with oxygen, explodes on the application 
of flame. 

Carbon disulphide corresponds in composition to carbon 
dioxide. 

CO^ carbon dioxide. 
CS^ carbon disulphide. 

It is also analogous to the latter body in its chemical func- 
tions. While carbon dioxide combines with metallic oxides, 
forming carbonates, carbon disulphide combines with metallic 
sulphides, forming sulphocarbonates. 

CO' + Na'O = Na^CO' corresponding to H'CO' 

Sodium oxide. Sodium carbonate. Carbonic acid 

(bypotlietical). 

CS^ + Na^S = Na^CS^ corresponding to H^CS^ 

Sodium sulpbide. Sodium sulphocarbonate. Sulphocarbonic acid. 

Sodium carbonate and sulphocarbonate possess the same con- 
stitution. By the action of strong acids they should give anal- 
ogous products : the one, carbonic acid, H'CO^ ; the other. 



216 ELEMENTS OF MODERN CHEMISTRY. 

sulphocarbonic acid, H^CSl The latter body is indeed formed 
under such circumstances, but normal carbonic acid, if it exist, 
possesses no stability, and at once decomposes into carbon diox- 
ide and water. 

Carbon disulphide is employed in the arts in the manufac- 
ture of vulcanized caoutchouc, and as a solvent for caoutchouc 
in the fabrication of goods impermeable to water by the deposit 
of a thin layer of that substance. It is also employed as a 
solvent for, and in the extraction of, fats and oils. 

CARBON OXYSULPHIDE. 

Density compared to air 2.1046 

Density compared to hydrogen 30.4 

Molecular weight CSO =60. 

This body was discovered by de Than in 1867. It is inter- 
mediate between carbon dioxide and carbon disulphide. 

COO carbon dioxide. 
CSO carbon oxysulphide. 
CSS carbon disulphide. 

Preparation.^ — It is prepared by decomposing potassium sul- 
phocyanide by dilute sulphuric acid. Potassium sulphate and 
hydrosulphocyanic acid are formed, and, in the presence of an 
excess of sulphuric acid and water, the latter decomposes into 
ammonia and the gas carbon oxysulphide which may be collected 
over mercury; the ammonia remains combined with the sul- 
phuric acid in the form of sulphate. 

CSNH + WO = NW + CSO 

Hydrosulphocyanic acid Carbon oxysulphide. 

Properties. — Carbon oxysulphide is a colorless gas, having 
an odor like that of carbon disulphide, but also recalling that 
of hydrogen sulphide. 

On contact with an incandescent body, even a match pre- 
senting a spark of fire, it takes fire, burning with a blue flame, 
and depositing sulphur if the supply of air be insufficient. 
With one and a half times its volume of oxygen it constitutes 
an explosive mixture. 

2 volumes of carbon oxysulphide . . = CSO mixed with 

3 volumes of oxygen =0^ yield 

2 volumes of carbon dioxide . . . . = CO^ and 

2 volumes of sulphur dioxide . . . . == SO^ 



COMPOUNDS OF CARBON AND HYDROGEN. 217 

Water dissolves about its own volume of carbon oxysulphide, 
but the solution decomposes in a few hours, with the formation 
of hydrogen sulphide and carbon dioxide. 

CSO -i- W0 = CO' + H'S 

Carbon oxysulphide is absorbed completely, but more slowly 
than carbon dioxide, by solutions of the alkaline hydrates ; by 
a reaction analogous to the preceding, a sulphide and a carbonate 
are formed. 

COMPOUNDS OF CARBON AND HYDROGEN. 

These compounds are numerous and important. Carbon 
unites with hydrogen in dififerent proportions, and the atoms of 
carbon and hydrogen may accumulate in considerable numbers 
in the molecules of their compounds. These combinations are 
called hydrocarbons or carbides of hydrogen. Hydrogen mono- 
carbide, or marsh gas, contains only one atom of carbon com- 
bined with four atoms of hydrogen ; its molecule is therefore 
represented by the formula CH*. In olefiant gas, or ethylene, 
two atoms of carbon are united with four atoms of hydrogen; 
in the volatile liquid known as benzine or benzol, which is ob- 
tained in large quantities from coal-tar, six atoms of carbon are 
combined with six atoms of hydrogen. Lastly, the molecule 
of oil of turpentine contains ten atoms of carbon and sixteen 
of hydrogen. 

Hence these substances give us the following formulae : 

CH* methane, or marsh gas. 
C'H* ethylene, or olefiant gas. 
C^H^ benzine. 
C'»H^« turpentine. 

These examples, which might be indefinitely multiplied, show : 
1st. That the atoms of carbon unite in various proportions with 
the atoms of hydrogen to constitute the molecules of the hydro- 
carbons. 2d. That they accumulate in greater or less numbers 
to form molecules more and more complex, that is, containing 
an increasing number of atoms of carbon and hydrogen. 

All of these bodies must be considered among the organic 
compounds ; indeed, the latter are nothing more than the com- 
pounds of carbon, and carbon monoxide and dioxide may also 
be properly considered as the most simple organic Gombinations. 
K 19 



218 



ELEMENTS OP MODERN CHEMISTRY. 



Hence if the most strictly rigorous method were adhered to, 
the description of the compounds of carbon and oxygen would 
be followed by that of all the other compounds of this element, 
that is, of all the organic compounds. However, for the pur- 
poses of study it is advantageous to treat the latter bodies 
separately, and they will be so considered in this work. The 
following experiments will expose some of the general proper- 
ties of the hydrocarbons which have been mentioned : 

1. If a lighted taper be applied to a jar of methane, which 
is also called marsh gas, because it is disengaged from the muddy 
bottoms of marshes, the gas takes fire and burns with a lumi- 
nous flame. 

2. If the same experiment be repeated with ethylene gas, 
which contains for the same proportion of hydrogen twice as 
much carbon as marsh gas, a still more luminous flame results. 

3. It is well known that benzine and turpentine take fire 
when lighted, and burn with bright flames ; but it is also known 

that their flames are smoky. 

The hydrocarbons are then 
combustible; and how could 
they be otherwise, since they 
contain only two combustible 
elements, carbon and hydro- 
gen? The products of the 
combustion are water and 
carbon dioxide, and the forma- 
tion of the latter gas may be 
proved by agitating the con- 
tents of the jars in which the 
combustion has taken place 
with lime-water; the latter 
immediately becomes milky 
by the precipitation of calcium 
carbonate. 

This combustion is more or 
less complete ; when the gas or 
vapor which burns contains a 
large amount of combustible elements, the oxygen of the air 
may not be present in sufiicient quantity to burn them ail, that 
is, to oxidize them completely. Under these conditions it is 
the hydrogen which is burned by preference, and the carbon 
partly escapes combustion. 




Fig. 86. 



STRUCTURE OF FLAME. 



219 



A flame is a gas or vapor in combustion. This combustion 
is an oxidation, and it is the oxygen of the air which is the 
agent. In order that it may take place, it is generally neces- 
sary that the combustible gas shall be brought to a high tem- 
perature; but once commenced, the combustion continues of 
itself, because the heat disengaged by 
the oxidation is sufficient to maintain the 
phenomenon. But if a flame be suddenly 
cooled, the combustion is at once arrested. 

A flame may be cooled by depressing 
into it a piece of fine wire gauze. The 
incandescent gases cannot pass through 
the meshes of the gauze without being 
cooled by contact with the metal, which 
is a good conductor of heat. For this 
reason, no combustion takes place above 
the gauze (Fig. 86). 

If a piece of wire gauze be held over 
an escaping jet of gas, the latter may be 
ignited above the gauze, and will burn 
without the combustion being propagated 
to the gas below ; the gauze acts as a 
screen, separating the jet into two portions, 
the lower cold and invisible, the upper in 
combustion and luminous. 

Sir Humphry Davy made a happy ap- 
plication of these facts in the construction 
of the miner's safety-lamp. This is an 
ordinary lamp surrounded by a cylinder 
of wire gauze (Fig. 87). 

Such a lamp gives less light than one 
not protected by an envelope, but it re- 
moves the danger of explosions of fire- 
damp, for when an explosive mixture is pj^ gy 
formed in the galleries of a mine, the gas 
may penetrate to the interior of the lamp and take fire there, 
but the flame cannot pass through the cooling envelope of wire 
gauze. The safety-lamps are now constructed with the lower 
part of the cylinder of glass, so that there is no diminution in 
the amount of light given. 

As the oxidation of combustible elements is the source of 
heat, it is evident that the different parts of a flame cannot be 




220 ELEMENTS OF MODERN CHEMISTRY. 

uniformly hot, for the oxygen of the surrounding air cannot 
equally attain all portions. The exterior borders are the most 
intensely heated; they are surrounded by air, and constitute 
the seat of combustion. From them the heat is radiated not 
only externally, but also to the interior of the 
flame, where it produces interesting phenomena. 
These may be studied by analyzing a flame, 
that is, considering separately the difi"erent parts 
of which it is composed. If the flame of a can- 
dle be examined, it will be found to present three 
distinct layers, or cones (Fig. 88). 

1. A dark central part, a, which surrounds 
i JiiA ^^^^ wick. This is known as the obscure cone, 

or cone of generation; its temperature is not 
high. 

2. A luminous part, bb\ surrounding the ob- 
scure cone. This is the centre from which the 
light is emitted. It is known as the luminous 
cone, or cone of decomposition. 

3. An exterior envelope, cc\ thin, and pro- 
ducing but little light, yellow towards the sum- 
mit, e, and bluish towards the base, dd'. It is the 
cone of complete combustion, and its temperature 
is the highest. 

It is easy to account for these phenomena. 
The material of the candle is melted by the heat 

Fig. SsT ^^ ^^^ flame, the liquid is drawn up into the 
wick by capillarity, and arrives at the incan- 
descent summit. There it is decomposed, producing gases and 
vapors rich in carbon and hydrogen, and which rise around the 
wick, forming an irregular cone. The gaseous products consti- 
tuting this cone do not present the same composition through- 
out. They have been analyzed by H. Sainte-Claire Deville, 
by the aid of very ingenious processes. 

The obscure cone is formed of gaseous products holding in 
suspension finely-divided carbon, which has not yet arrived at 
incandescence. 

These products become heated on reaching the more central 
portions of the flame. Then the carbon, which is set free by 
the decomposition of gases rich in carbon, is brought to bright 
incajidescence, but it is completely burned only when it reaches 
the exterior envelope, where the oxygen is in excess. A simple 



STRUCTURE OF FLAME. 



221 



experiment will demonstrate that the most luminous portion 
of the flame holds in suspension finely-divided and incandes- 
cent carbon. If a porcelain saucer be depressed into this 
portion, the carbon will be deposited on the vessel in the form 
of soot. 

It is this solid and incandescent carbon which causes the 
luminosity of the flame. The flame of hydrogen, which con- 
tains only gaseous products, is pale. In the calcium or Drum- 
mond light it produces great brilliancy because a solid body, 
lime, is heated to bright incandescence. When the carbon 
suspended in a flame is in excess in proportion to the supply 
of oxygen, it is incompletely burned, and is carried into the 
air. The flame then smokes. 

At the base of the cone, carbon monoxide and methane, the 
first products of the decomposition of the candle, burn on con- 
tact with the air at dd' with a bluish flame. 

According to recent experiments, the density of a burning 
gas is not without influence upon the lustre of the flame. The 
flame of hydrogen is luminous when that gas is burned under 
strong pressure (Frankland). 

Illuminating gas is a mixture of hydrogen with various gas- 
eous hydrocarbons and a small proportion of carbon monoxide. 
It is manufactured by the destructive dis- 
tillation of bituminous coal. The aqueous 
products containing ammonia, and the 
tarry matters formed during the distilla- 
tion are condensed, and the gas is purified 
by washing with water and passage over 
slaked lime to remove sulphur and other 
impurities. 

Illuminating gas forms an explosive 
mixture with air, but if the mixture be 
burned as it is formed, the resulting flame 
will be almost colorless and will deposit 
no soot, the whole of the carbon coming- 
in contact with sufiicient oxygen for its 
complete combustion. These conditions 
are fulfilled in the Bunsen burner (Fig. 
89). In this burner, the force of the 
escaping gas-jet draws in air through holes immediately oppo- 
site the jet in a wider tube, at the end of which the mixture is 
burned. 

19* 




Fig. 89. 



222 



ELEMENTS OF MODERN CHEMISTRY. 



GENERAL NOTIONS UPON THE METALLOIDS. 



THEORY OF ATOMICITY. 

From a consideration of the facts acquired in the study of 
the elements known as metalloids, we may deduce certain gen- 
eral consequences, and while looking back on the field over 
which we have passed, we may at the same time fix certain 
landmarks for the remainder of our course. 

The elements which we have studied are not alike in their 
aptitude to enter into combination, nor in the general characters 
of their compounds. In this respect, analogies and differ- 
ences have been established between them, and these have 
become the basis of a rational classification. Following the 
example of Dumas, we have arranged these elements in groups 
or families, uniting in the same group those which are related 
by their chemical functions. For this reason boron has been 
separated from silicon and carbon, since it differs from them 
so far as concerns the composition of their compounds. The 
groups thus formed are as follows : 



HYDROGEX. 


OXYGEN. 


NITROGEN. 


BORON. 


SILICON. 




SULPHUR. , 


PHOSPHORUS. 




CARBON, 


FLUORINE. 


SKLENIUM. 


ARSENIC. 






CHLORINE. 


TELLURIUM. 


ANTIMONY. 






BROMINE. 










IODINE. 











In order to account for the chemical functions of all these 
bodies, that is, for the parts which they play in their combina- 
tions, we must first consider their hydrogen compounds. They 



constitute the following series 



HH 


H^O 


ffN 


H*Si 


Hydrogen. 


Water. 


Ammonia. H3 


'drogen silicide. 


HCl 


H^S 


H^P 


H^C 


Hydrochloric 
acid. 


Hydrngpn 
sulphide. 


Hydrogen 
pbospLidc. 


Hydrogen 
carbide. 


HBr 


H^Se 


H^^As 




Hydrobromic 
acid. 


Hydrogen 
seleuide. 


Hydrogen arsenide. 




HI 


H^Te 


H=^Sb 




Ilydriodic acid. 


Hydrogen 
telluride. 


Hydrogen antimonide. 




HFl 








Hydrofluoric acid. 









THEORY OF ATOMICITY. 223 

It is seen that the preceding groups are characterized by the 
composition of their hydrogen compounds. While the bodies 
of the first group combine with hydrogen atom for atom, those 
of the second group require two atoms of hydrogen, those of 
the third three, and those of the fourth four, to form hydrogen 
compounds. Hence we may draw the conclusion that the atoms 
of these metalloids are far from being equivalent in their power 
of combination with hydrogen. 

The atoms of chlorine, bromine, and iodine are equivalent 
to each other in this respect, for each requires but one atom 
of hydrogen. 

The atoms of oxygen, sulphur, etc., are equivalent to each 
other, for each combines with two atoms of hydrogen. 

The atoms of nitrogen, phosphorus, arsenic, and antimony 
are equivalent to each other, for each of them unites with three 
atoms of hydrogen. 

Lastly, the atoms of carbon and silicon are equivalent, for 
each can unite with four atoms of hydrogen. 

But, on the other hand, it is evident that the atoms of chlo- 
rine, oxygen, nitrogen and carbon are not equivalent to each 
other, as regards their power of combination with hydrogen, 
since each of them unites with a diflferent number of atoms of 
that body. 

In this respect it may be said that 

1 atom of chlorine is equivalent to 1 atom of hydrogen. 
1 atom of oxygen " 2 atoms " 

1 atom of nitrogen " 3 atoms " 

1 atom of carbon *' 4 atoms " 

It is evident that the capacity of combination which resides 
in the atoms of simple bodies and by which they attract the 
atoms of hydrogen, is unequal. Leaving aside its intensity, 
this force is exerted in different degrees, for it determines the 
union of 1 atom of chlorine, oxygen, nitrogen, or carbon, with 
1, 2, 3, or 4 atoms of hydrogen. 

This number of hydrogen atoms is the measure of the degree 
of force which resides in the atoms, — of the capacity of combi- 
nation which they possess for each other. 

Hence we conclude that 

The atoms of chlorine and its associates are monatomic or univalent. 
The atoms of oxygen '* " diatomic or bivalent. 

The atoms of nitrogen " " triatomic or triualent. 

The atoms of carbon " " tetratomic or quadrivalent. 



224 ELEMENTS OF MODERN CHEMISTRY. 

The capacity of combination which resides in the atoms, and 
which is exerted in such different manners according to the 
nature of the atoms, is called atomicity. Atomicity is the 
relative equivalence of the atoms; it is simple or multiple, and 
if we consider it in its first degree, we may say that the atoms 
of chlorine and the atoms of hydrogen are so constituted that 
a single atom of one attracts a single atom of the other. When 
they combine, they exchange in some manner a unit of satura- 
tion, and in the combination of chlorine and hydrogen two of 
these units of force are neutralized ; two units of saturation or 
two atomicities are exchanged: the atoms of chlorine and of 
hydrogen are univalent. 

The force which resides in an atom of oxygen is more com- 
plex. It attracts two atoms of hydrogen, and represents the 
second degree of capacity of combination, and we may say that 
in each atom of oxygen reside two atomicities, which are satis- 
fied and exchanged when this atom combines with two atoms of 
hydrogen. Hence, four atomicities are satisfied by the com- 
bination. 

Following the same reasoning, we consider that a triple capa- 
city of combination is active in an atom of nitrogen when this 
atom unites with three atoms of hydrogen ; and that six atom- 
icities are satisfied by the combination. 

Lastly, tetratomic carbon is provided with four atomicities, 
which are satisfied by the four atomicities which reside in four 
atoms of hydrogen. 

If this neutralization or exchange of two units of saturation 
be represented by a hyphen, we will have the following formulae : 



H-Cl 


H-O-H 


H 




H 


Hydrochloric acid. 


Water. 


1 

N 

/\ 

H H 




H-C-H 

1 
H 






Ammonia. 


H; 


ydrogen monocarbide. 



It is seen that in the formulae for water, ammonia and hydro- 
gen monocarbide, the polyatomic elements, oxygen, nitrogen 
and carbon, constitute, as it were, the nuclei around which the 
other atoms are symmetrically grouped. 

A great many other bodies present the same constitutions as 
the preceding ; it is evident that a given element in any com- 
pound may be replaced by another element having the same 
atomicity, without disturbing the equilibrium of the atomicities. 



THEORY OF ATOMICITY. 225 

Indeed, if we suppose the chlorine, oxygen, nitrogen, and 
carbon to be replaced by elements of corresponding atomicities, 
we will have the series of hydrogen compounds already con- 
sidered. All of the bodies which are classed together in the 
series belong to the same type. Each contains an equal num- 
ber of atomicities for the same number of atoms. 

According to the principle of substitution announced above, 
it is evident that the hydrogen in each of the hydrogen com- 
pounds under consideration may be replaced by another mon- 
atomic element, and the compounds thus formed will still belong 
to the primitive types. 

So considered, a great number of compounds possess the 
same constitution, — that is, the same molecular structure, — 
as hydrochloric acid, water, ammonia, and methane or hydro- 
gen monocarbide. Such are those arranged in vertical columns 
in the following table : 



Type HCl 


Type H20 


TYPENH3 


Type H* 


Cl-Cl 


H-O-H 


K 


CI 


Free chlorine. 


Water. 


1 


1 






N 


Cl-C-Cl 






/\ 


1 






H H 


CI 




Potassium amide. 


Carbon tetrachloride. 


K-Cl 


Cl-O-Cl 


CI 


CI 


Potassium chloride. 


Hypochlorous oxide. 


1 


1 






P 


Cl-Si-Cl 






/\ 


1 






CI CI 


CI 




Phosphorus trichloride. 


Silicon tetrachloride. 


K-I 


H-O-K 


CI 


H 


Potassium iodide. 


Potassium hydrate. 


1 


1 






Sb 


H-Si-H 






/\ 


1 


Ag-I 


Ag-O-Ag 


CI CI 


H 


Silver iodide. 


Silver oxide. Ant 


imony trichloride 


. Hydrogen silicide. 



All of these bodies belong to the respective types HCl, H^O, 
NH^, CH*, the first three of which were established by Ger- 
hardt, and have their existence explained by the atomicity of 
the elements ; that is, by the varying equivalence of their atoms, 
measured, in the present examples, by the number of hydrogen 
atoms with which they combine. 

One atom of oxygen is equivalent to two atoms of hydrogen 



226 ELEMENTS OF MODERN CHEMISTRY. 

or two atoms of chlorine. Hence, in the preceding combina- 
tions, two atoms of chlorine may be replaced by one atom of 
oxygen without changing the equilibrium of the atomicities. 
Thus, the oxides SiO^CO'^, correspond to the chlorides SiCP, 
CCP, and belong to the same type. The four atomicities of 
an atom of silicon or carbon are saturated by the four atomici- 
ties of two atoms of oxygen. 

The trichlorides of phosphorus and antimony, POP and SbCP, 
which will be found in the preceding table, require an impor- 
tant remark. They are not saturated with chlorine, and each 
may combine with two more atoms of that element, producing 
the compounds POP and SbCP. 

Thus, while phosphorus exhausts its power of combination 
with hydrogen in uniting with three atoms of that element in 
PH^, its capacity of combination with chlorine is only exhausted 
when it has combined with five atoms ; while it plays the part 
of a triatomic element in hydrogen phosphide, it is pentatomic 
in phosphorus pentachloride. 

From these facts it follows that it is often difficult to meas- 
ure in an absolute manner the capacity of combination which 
resides in an atom ; for that capacity varies according to the 
nature of the elements upon which it is exerted. Af&nity is 
an elective force. A given element does not attract all of the 
other elements with equal facility ; it selects certain ones by 
preference, and neglects the others. With one, it may form 
but a single compound; with another, it may form several. 

Nitrogen forms with hydrogen but one combination, ammo- 
nia, NH*, which cannot fix any more atoms of hydrogen. Sat- 
urated with hydrogen in ammonia, nitrogen manifests in con- 
tact with that element but three atomicities. But let ammonia 
be brought in contact with a body other than hydrogen, hydro- 
chloric acid, for example, and it will combine with it, forming 
ammonia hydrochloride, or ammonium chloride. If its ca- 
pacity of combination is exhausted for hydrogen, HH, it is 
not exhausted for hydrogen combined with chlorine, HCl. 
Thus, an atom of nitrogen possesses other affinities than those 
which it manifests for hydrogen in ammonia. AVhile nitrogen 
is triatomic in ammonia because it is united with three mon- 
atomic atoms, it behaves as a pentatomic element in ammonium 
chloride. 

The parts which polyatomic elements play in their compounds 
may be expressed by accents marking the number of atomici- 



THEORY OF ATOMICITY. 227 

ties or tlie quantivalence of the element, as shown in the 
following formulae : 

0"H^ WW WWQ\ F"CP P^CP C'^O"^ 

Water. Ammonia. Ammonium Phosphorus Phosphorus Carbon 
chloride. trichloride, pentachloride. dioxide. 

In these compounds, as has been remarked before, the poly- 
atomic elements form, as it were, the nuclei around which the 
other elements are grouped. This is an important idea, since 
it leads to the determination of the constitution of the mole- 
cules, that is, the arrangement of their atoms. The considera- 
tions just presented concerning the functions of the elements 
in compounds alone permit the resolution of this question ; 
they alone lead to the discovery of the relations existing be- 
tween the atoms in their combinations, and to the determina- 
tion of their relative positions, in a word, to the revelation of 
the molecular structure. 

The following developments will demonstrate this fact. 

We will reconsider certain of the combinations above men- 
tioned, which have been taken as types. 

In water, an atom of diatomic oxygen fixes two atoms of 
hydrogen. One atom of oxygen can fix two atoms of any 
monatomic element, forming compounds belonging to the same 
type as water; but it cannot at the same time fix a monatomic 
element and a diatomic element. In other words, an atom of 
hydrogen in water may be replaced by an atom of chlorine, 
bromine, iodine, or potassium, but not by an atom of oxygen ; 
and if a second atom of the latter element be joined to the 
oxygen of water, it will be seen that there remains a free affin- 
ity which may be satisfied by hydrogen. Hydrogen dioxide 
would result. 

H-0"-H H-0"-0"-H 

Water. Hydrogen dioxide. 

Hence, we draw the conclusion that in hydrogen peroxide, 
the two atoms of oxygen are combined with each other, and 
that in uniting together each atom loses one atomicity, the two 
others being satisfied by hydrogen. 

The same considerations are applicable to the compounds of 
chlorine and oxygen. 

Hypochlorous acid may be regarded as composed of an atom 
of chlorine united to the group hydroxyl. 
Cl-0"-H = Cl(OH)' 

Hypochlorous acid. 



228 ELEMENTS OP MODERN CHEMISTRY. 

In this compound the chlorine exchanges one unit of satu- 
ration with the oxygen of the group OH, just as it exchanges 
one with hydrogen in hydrochloric acid: it is monatomic or 
univalent. In chloric acid it is combined with two atoms of 
oxygen and one group, OH. It exchanges 4 atomicities with 
oxygen, and one with the group OH : 

CW'XOHj' 

Chloric acid. 

Chlorine thus manifests 5 atomicities in chloric acid ; but it 
has 7 in perchloric acid. 

C1-'03(0H)' 

Perchloric acid. 

Without dwelling on these considerations, we will take one 
more example. 

In hydrogen phosphide, one atom of phosphorus is combined 
with three atoms of hydrogen ; it manifests but three atomici- 
ties, and these could not neutralize those which reside in three 
atoms of oxygen, since the latter possess six atomicities. If, 
then, three atoms of diatomic oxygen were united with one 
atom of triatomic phosphorus, it is clear that three affinities 
would remain free, one in each of the three atoms of oxygen. 
In phosphorous acid, these three affinities of the oxygen atoms 
are satisfied by three atoms of hydrogen. We may suppose 
that in the molecule of this compound, the phosphorus is the 
nucleus around which are grouped three atoms of oxygen, each 
of which is joined also to one atom of hydrogen. 

This atomic grouping is indicated in the following formulae : 

H OH 

I I 

P P 

H^H HO^OH 

Hydrogen phosphide. Phosphorous acid. 

This hydrogen, combined with the oxygen in all of the oxy- 
gen acids, plays invariably the same part: it saturates the one 
atomicity which remains free in one atom of oxygen. The 
oxygen thus combined with an atom of hydrogen, has lost one 
of its atomicities by the fact of this combination ; it still retains 
one in the group OH, which represents, as it were, water less 
one atom of hydrogen. 

HOH — H = (OH)' 



THEORY OF ATOMICITY. 229 

This group is named hydroxyl, and it is evident that, 
although it cannot exist by itself, it may play the part of a 
monatomic element, for it retains one free atomicity. It may 
then replace a monatomic element, such as hydrogen or chlo- 
rine. Indeed, it plays an important part in the constitution of 
acids. 

If we consider the examples which have already been dis- 
cussed, we will notice that it is this hydroxyl which, by com- 
bining with an element or group of elements capable of forming 
acids, confers upon them the characters of acids. So consid- 
ered, hypochlorous acid is formed by the union of hydroxyl 
with an atom of chlorine. 

Cl(OH)' 

Hypochlorous acid. 

Sulphuric acid is formed by the union of two hydroxyl groups 
with sulphurous oxide, and represents in a manner sulphuryl 
chloride in which the two atoms of chlorine are replaced by 
two hydroxyl groups. 

Sulphuryl chloride. Sulphuric acid. 

Phosphorous acid is formed by the union of three hydroxyl 
groups with one atom of phosphorus. 

CI r (OH)' 

CI F" ] (OH)' 

(CI ((OH)' 

Phosphorus trichloride. Phosphorous acid. 

Lastly, phosphoric acid results from the union of three hy- 
droxyl groups with one atom of phosphorus already combined 
with one atom of oxygen (phosphoryl). 

( CI ( (OH)' 

0"P^ CI 0"P^^ (OH)' 

(CI ((OH)' 

Phosphoryl trichloride. Phosphoric acid. 

Such, according to the theory of atomicity, are the relations 
existing between the atoms of certain acids ; such, in other words, 
is the constitution of these acids. It would be easy to extend 
these considerations to other bodies, but the examples we have 
chosen are sufficient to indicate the importance of the idea of 
atomicity, when it is applied to the discovery and definition of 

20 



I 



230 ELEMENTS OP MODERN CHEMISTRY. 

the part played by each element in a given compound. By 
supposing the capacities of combination of chlorine, oxygen, 
sulphur, and phosphorus to be known, we have been able to 
follow these bodies in their most important combinations, we 
have seen how they attract and group around themselves other 
elements. We have thus been able to penetrate the atomic 
structure of the molecules, and have built up as it were the 
molecular edifice. It must be remembered, however, that the 
preceding formulas do not in any manner represent the real 
positions of the atoms in space. Their sole object is to indi- 
cate the points of attachment of the affinities, and consequently 
the mutual relations between the atoms. 



METALS. 



The metals are elements which are good conductors of heat 
and electricity, and are endowed with a peculiar lustre, which 
is called the metallic lustre. This definition, it will be ob- 
served, is founded upon certain physical characters rather than 
upon chemical properties. It is unsatisfactory and wanting in 
exactness, for it is applicable to bodies which are properly con- 
sidered as metalloids. Such is antimony, which has already 
been described, and bismuth, which should be placed beside 
antimony. Indeed, the distinction between the metals and 
metalloids is not so well marked that a line which shall sepa- 
rate these two classes of simple bodies may be sharply drawn. 

Physical Properties of the Metals. — These will be found 
in the table on page 232, but the indications there given may 
be completed by certain other developments. 

The metals are opaque, but their opacity is not absolute. 
A sheet of gold-leaf pressed out between two plates of glass 
allows the passage of a green light. 

Grold possesses a brilliant lustre and a yellow color, but it 
loses this lustre when it is reduced to a minute powder. When, 
however, this powder is rubbed with a hard body, when, for 
example, it is triturated in an agate mortar, or passed under 
the burnisher, it acquires a certain degree of cohesion, and 
again assumes its lustre. 

It is thus with all the metals. They lose their metallic lustre 
when finely divided and reassume it on burnishing. 

The yellow color of gold is not its true color ; the rays which 
reach the eye are the result of but one reflection, but if light 
be successively reflected from ten surfaces of gold, the metal 
will appear of a bright-red color. Under the same circum- 
stances, copper will appear scarlet, zinc indigo, iron violet, and 
silver pure yellow (B. Pre vest). 

Most of the metals may be crystallized. Bismuth is the 
most striking example. If a few kilogrammes of pure bismuth 
be fused, and the liquid mass be allowed to cool slowly, the 

231 



232 



ELEMENTS OF MODERN CHEMISTRY. 




••••§. 

. . . . T s, . . . 


. 8.79 
. 8.60 
. 7.79 
. 7.79 
. 7.25 
. 7.29 
, 7.20 
. 7.01 

. 6.71 
. 2.56 
. 0.97 

. 0.59 


1 . .-^ . . . . 
i al £. .ipi 


r (cast) . 
ium . . 
t (cast) . 

5 malleable 

I cast . 
ast) . . . 
anese . . 
Qium . . 
cast) . . 
loiiy . . 

nium . . 

sium . . 
im . . . 



^ a 



o O S a< J 



;?; t u o 



a 

a 2 



GENERAL PROPERTIES OF METALS. 



233 



metal will solidify first next to tlie walls of the vessel and on 
the surface, where it is most cooled. If, in a little while, the 
crust which covers the still liquid metal be pierced, and the 
latter be poured out, the whole of the interior of the vessel 
will be found covered with magnificent crystals, arranged in 
hopper-like pyramids, and presenting brilliant, rainbow-hke 
colors. 

Other metals, such as copper, lead, antimony, tin, silver, and 
gold, may be crystallized under certain conditions. Some of 
the metals are found crystallized in nature. 

Those metals which may be beaten or rolled into thin laminae 
are said to be malleable. A A (Fig. 90) represent two steel 




Fig. 90. 

rollers capable of moving on their axes in opposite directions. 
A plate of metal engaged between them will be drawn in, and 
the rolled sheet will pass out on the other side with a uniform 
thickness equal to the distance between the two rollers. By 
diminishing this distance more and more by means of the 
screws BB, the sheet may gradually be reduced in thickness. 

Metals which may be drawn out into wires are said to be 
ductile. The wire-drawing machine is represented in Fig. 
91. It consists of a steel plate, //, firmly fixed in the up- 
rights CC, which are themselves solidly attached to a bench. 
The plate is pierced with a series of holes regularly decreasing 
in diameter. The wire is drawn from the bobbin A, through 
the holes and around the cylinder B, which is moved by power. 

That a metal may be drawn into fine wires, it is necessary 
that it shall ofi"er a certain resistance to rupture. This is called 
the tenacity of the metal. It is measured by suspending weights 

20* 



234 



ELEMENTS OF MODERN CHEMISTRY. 



at the extremities of wires of the same diameter. Iron is the 
most tenacious of metals. 

All of the metals are fusible. Some of them are volatile 
and may be distilled ; among the latter are mercury, potassium, 
sodium, zinc, and cadmium. All of the metals are insoluble. 

Chemical Properties of the Metals. — The metals combine 
with each other and with the metalloids, the energy with which 
these combinations take place being very variable. In general, 




Fig. 91. 



the metals having the strongest affinities are those known as the 
alkaline metals, because they are obtained from the alkalies. 
Such are potassium and sodium. 

All of the metals combine directly with chlorine. The chlo- 
rides thus formed do not all possess the same composition ; they 
contain for one atom of metal a varying number of chlorine 
atoms. 

A similar remark applies to the oxides and sulphides formed 
by the union of oxygen and sulphur with the metals. The 
power of combination of the latter with chlorine, sulphur, oxy- 
gen, etc., is far from being the same. In other words, the atoms 
of the metals combine unequally with the atoms of chlorine, 
oxygen, etc. ; hence it follows that the atomic composition of 
the bodies thus formed is different. If the metals be compared 
together in this respect, analogies and differences will be estab- 
lished between them, which become the basis for a rational 
classification. Those metals which form compounds having 



EXTRACTION OF METALS. 235 

analogous atomic constitutions are put into the same group. 
Sucli principles as these have guided us in the classification of 
the metalloids, and we will apply them to the metals as soon as 
we have acquired a general knowledge of their compounds. 

Thenard founded a classification of the metals, not upon their 
power of combination considered in a general manner, but upon 
the variable energy of their affinities for oxygen. He measured 
this affinity: 

1. By the facility with which the metals attract free oxygen 
at various temperatures. 

2. By the difficulty with which the oxides, once formed, 
abandon their oxygen. 

3. By the greater or less energy with which the metals de- 
compose water. 

Following these principles, Thenard divided the metals into six 
classes. It cannot be denied that this classification presents many 
practical advantages, but, on the other hand, in a great num- 
ber of cases it does not recognize the best established analogies. 

Natural State and Extraction of the Metals. — Certain 
metals are found in nature free from all combination. It is 
thus that gold, silver, copper, bismuth, etc., are met with in 
the native state. 

More often the metals are found combined with oxygen, sul- 
phur, or other metalloids. The natural sulphides are numerous 
and abundant : those of silver, copper, mercury, lead, and zinc 
constitute the minerals from which these metals are ordinarily 
extracted. 

Iron and tin are obtained from their oxides, which are found 
in nature. 

The metals are often found in saline combinations, in the form 
of chlorides, carbonates, sulphates, phosphates, and silicates. 

We can only indicate here in a very general manner the 
methods by the aid of which the metals are extracted from 
their combinations. 

If a metal is to be obtained from its oxide, the latter is 
reduced by charcoal at a high temperature. 

If the ore be a sulphide, it is first roasted, that is, heated in 
contact with the air. The oxygen of the air then acts upon 
the sulphur, which is disengaged in the form of sulphurous 
oxide, and upon the metal, which remains in the form of oxide ; 
the latter is afterwards reduced by charcoal. 

The metals are sometimes obtained from their chlorides by 



236 ELEMENTS OF MODERN CHEMISTRY. 

heating the latter with sodium, which combines with the chlo- 
rine, forming sodium chloride. 

ALLOYS. 

The combinations of the metals with each other are called 
alloys; amalgams are the alloys formed by mercury. These 
combinations take place with the production of heat. 

If a small quantity of mercury be heated in a crucible or a 
capsule, and a morsel of sodium be thrown into it, the latter 
dissolves instantly with a hissing noise, which indicates the 
disengagement of heat. 

By employing the proper proportions of mercury and so- 
dium, the alloy may be obtained in crystals possessing a definite 
composition. 

Crystalline combinations of zinc and antimony are known. 
The most interesting, Sb-^Zn^, contains two atoms of antimony 
for three atoms of zinc. 

It is necessary to state that more generally the alloys do not 
present the characters of definite compounds. The metals seem 
to alloy each other in all proportions, forming mixtures which 
are more or less homogeneous ; but this is only in appearance, 
and it must be admitted that one or more compounds exist in 
such a mixture, remaining dissolved in each other, or mixed 
with the excess of one of the metals. Such a mixture would 
form a sensibly homogeneous mass, especially when the molten 
mixture had been suddenly cooled. But if the cooling be slow, 
it may happen that the less fusible definite compounds separate 
from the mixture in the crystalline form, leaving the more 
fusible compounds which still remain liquid. Such a separa- 
tion often takes place in large masses of melted alloys which 
are allowed to cool slowly. The process is called liquation, 
and it may be readily conceived that the alloys so cooled are 
far from homogeneous in composition after their solidification. 

Beciprocally, when a mass composed of a mixture of metals 
and alloys is slowly heated, the more fusible assume the liquid 
state first, and separate from the others. 

This difference between the fusing-points of the various defi- 
nite compounds which may exist in an alloy is taken advantage 
of in the arts for their separation. 

Alloys are always more fusible than the most fusible of their 
component metals. 



ALLOYS. 237 

There is an alloy whicli is fusible between 66 and 71° ; it is 
formed of 

Cadmium 1 to 2 parts. 

Tin 2 parts. 

Lead 4 parts. 

Bismuth 7 to 8 parts. 

This is known as Wood's alloy. The fusible metal of Arcet 
is composed of 

Bismuth 8 parts. 

Lead 6 parts. 

Tin 3 parts. 

It melts at 94.5°. The following table gives the composition 

of the principal alloys : 

^ ,, . (Gold 900 

^^1^««^^ i Copper 100 

,,,,.,. f Gold 750-920 

««^^J«^«'^y i Copper 250-80 

Q., . (Silver 900 

Silver coin -^ ^ -i^,. 

[ Copper 100 

Q., , . (Silver 950 

S^^^^^P^^*^ {copper 50 

o-, . , f Silver ....... 800 

Silver jewelry . n,^^,. 



( Copper 200 

r Copper 93.5-95 

Bronze medals < Tin 6-4 

( Zinc 0.5-1 

100 

10 

Bell-metal | S?.PP"^' 15 



Gun-metal | ^fPP^'' 



Tin 22 



Bed brass 



Speculum-metal j Tm^^' 33 

Aluminium bronze { a7^'' • ^V? 

( Aluminium 10-5 

f Copper 90 

(Zinc 10 

White brass j 5«PP«^ 65 

( Zinc 35 

{Copper 50 

Zinc 25 

Nickel 25 

Lead 80 

.... 20 

Tin 100 

Britannia-metal U"^''"^^ ? 

Bismuth 1 

[ Copper 4 

Tin 92 

.... 8 

Tin 82 

.... 18 



Type-metal \ a. \- ' ' 

•' ^ I Antimony 



Hard pewter j ^'^^^ 



Soft pewter j T rl 

(Tin 



Plumbers' solder 



Lead 33 



238 ELEMENTS OF MODERN CHEMISTRY. 



METALLIC OXIDES AND HYDRATES. 

Formation of Metallic Oxides. — The metals absorb oxygen 
with very unequal energy. Many of them become oxidized 
when exposed to the air at temperatures more or less elevated. 
In this respect it is important to distinguish the action of dry 
air from that of moist air. 

Potassium is the only metal that absorbs dry oxygen at ordi- 
nary temperatures. All of the other metals, with the excep- 
tion of silver, gold, and platinum, only become oxidized in the 
air at very high temperatures. Melted lead absorbs oxygen. 
Mercury becomes oxidized at about 350° ; copper at a dull-red 
heat. 

The combination often takes place with the production of 
luminous heat. Iron burns in oxygen, but it is necessary that 
the metal be first heated to bright redness that the combustion 
may take place. 

However, the finely-divided iron that is obtained by reducing 
oxide of iron in a current of hydrogen at a comparatively low 
temperature, will take fire when exposed to the air at ordi- 
nary temperatures. It is pyrophoric, and the fine state of 
division of the metal favors the oxidation. If the powder be 
projected into the air, each particle takes fire and burns with a 
bright flash. 

A bright sheet of iron will indefinitely preserve its brilliant 
surface in dry air, but if a drop of water be placed upon it, or 
if it be exposed to the action of a moist atmosphere, rust makes 
its appearance in a short time. This rust is ferric hydrate, 
for the metal has at the same time absorbed oxygen and 
water. 

It is generally admitted that it is the oxygen of the air dis- 
solved in the water that first fixes upon the metal, and that 
the combination is favored by the presence of carbon dioxide. 
However it may be, the spot of rust once formed constitutes a 
Voltaic couple with the iron itself, and the current so estab- 
lished decomposes the water. The oxidation then proceeds 
rapidly, the oxygen of the decomposed water combining with 
the metal. 

It is possible that hydrogen dioxide may play a part in oxi- 
dations ; it may be formed as a secondary product during the 



METALLIC OXIDES AND HYDRATES. 239 

decomposition of the water, and fix directly upon the metals, 
converting them into hydrates (Weltzien). 

Fe^ + 3H=^0' = Fe^O^H^ 

Iron. Hydrogen dioxide. Ferric liydrate, 

Mg -f- H^O' = MgO'H^ 

Magnesium. Magnesium hydrate. 

Indeed, the oxidation of metals in moist air always produces 
hydrates and not oxides. 
Composition and Classification of the Oxides. — It has 

already been remarked that the metals differ as to the number 
of oxygen atoms with which they combine ; besides this, the 
same metal may form several compounds with oxygen ; differ- 
ent degrees of oxidation. Hence the oxides present different 
compositions, and the differences are important, since they exer- 
cise a marked influence upon the properties of the compounds. 

1. Certain oxides present the same atomic constitution as 
water. Two atoms of metal are combined with one atom of 
oxygen. 

K^O potassium oxide. 
Na^O sodium oxide. 
Li^O lithium oxide. 
T120 thallium oxide. 
Ag'^^O silver oxide. 

2. One atom of certain metals can combine with one atom 
of oxygen ; the oxides of the general formula MO result. 

BaO barium oxide. 
SrO strontium oxide. 
CaO calcium oxide. 
MgO magnesium oxide. 
MnO manganous oxide. 
FeO ferrous oxide. 
ZnO zinc oxide. 
PbO lead oxide. 
CuO cupric oxide. 
HgO mercuric oxide. 
SnO stannous oxide. 

The metallic oxides containing but one atom of oxygen are 
generally energetic bases ; that is, they react energetically with 
the acids, forming salts. They are sometimes called basic oxides. 

3. The sesquioxidcs are those which contain two atoms of 
metal and three atoms of oxygen. Such is antimony oxide, 
that has already been studied ; the oxides of bismuth, gold, etc., 
present an analogous composition. 



240 ELEMENTS OF MODERN CHEMISTRY. 



Sb^O^ antimony sesquioxide. 
Ei203 bismuth sesquioxide. 
Au^QS gold sesquioxide. 



Fe^O-^ ferric oxide. 
Mn'^QS manganic oxide. 
Ci^QS chromic oxide. 
APQS aluminium oxide. 



4. A large number of oxides contain two atoms of oxygen. 



BaO^ barium dioxide. 
Sr02 strontium dioxide. 
Mn02 manganese dioxide. 
PbO'^ lead dioxide. 



SnO''^ stannic oxide. 

The first four dioxides are incapable of uniting with acids to 
form corresponding salts. Dumas called them singular oxides. 
When manganese dioxide is heated with sulphuric acid, oxygen 
is disengaged, and manganous sulphate is formed, which corre- 
sponds not to the dioxide, but to manganous oxide. 

H'^SO* + MnO^ :=r MnSO* + H^O + O 

Sulphuric acid. Manganese dioxide. Manganous sulphate. 

Under the same circumstances, the other singular oxides act 
in the same manner. 

As to stannic oxide, it is the anhydride of a metallic acid. 

SnO^ + H^O = ff SnO^ 

Stannic acid. 

5. The oxides which contain three atoms of oxygen possess 
acid characters still more marked than stannic oxide. Man- 
ganese trioxide, MnO^, is known. Ferric and chromic anhy- 
drides present the same composition. 

MnO^ manganese trioxide, or manganic anhydride. 
CrO^ chromium trioxide, or chromic anhydride. 
FeQS iron trioxide, or ferric anhydride. 

6. There is a class of oxides still more complex than the 
preceding; they can be regarded as formed by the union of 
two oxides, and they have been named saline oxides. Such are 

Manganoso-manganic oxide Mn^O* = Mn^O^ -(- MnO, or red oxide of 

manganese. 
Diplumboso-plumbic oxide Pb'^O* = PbO^ + 2PbO, or red oxide of lead. 

The first contains one molecule of a sesquioxide, combined 
with one molecule of a monoxide ; the second, one molecule of a 
dioxide and two molecules of a monoxide. 



METALLIC OXIDES. 



241 



Chemical Properties of the Oxides. — Some of the oxides 
are fixed, that is, undecomposable by heat; others lose the 



whole or a part of their oxygen at temperatures more or less 
elevated. The oxides of the noble metals, such as silver, gold, 
and platinum, are decomposed by heat alone into metal and 
oxygen. We have seen that mercuric oxide is decomposed by 
a dull-red heat. Many of the oxides that contain two or three 
atoms of oxygen lose a part of the latter element when heated 
to redness. Such are the dioxides of manganese, lead, and 
barium. 

-The oxides containing but one atom of oxygen are among 
the most stable. Some of them absorb oxygen when they are 
heated in contact with air, forming higher oxides. Among 
these are manganous, ferrous, plumbous, and stannous oxides. 

Hydrogen reduces the greater number of the oxides at tem- 
peratures more or less elevated ; water is formed, and the metal 
is set at liberty. 

If a current of dry hydrogen be passed over ferric oxide 
heated in a glass bulb (Fig. 92), the oxide is reduced, and a 




Fig 



black powder is obtained which is finely divided and pyropho- 
ric iron. Vapor of water escapes at the same time by the 
drawn-out point of the bulb. 



Ferric oxide. 



3H^0 -L 2Fe 

Iron. 



21 



242 



ELEMENTS OF MODERN CHEMISTRY. 



The ferric oxide may be replaced by cupric oxide, CuO. If 
this oxide be heated in a current of hydrogen, it is reduced, 
and the action is so energetic that it gives rise to the produc- 
tion of luminous heat. 

Carbon reduces the greater number of the oxides with for- 
mation of either carbon dioxide or monoxide. It is even more 
energetic in its action than hydrogen, for it decomposes oxides 
which are irreducible by the latter element, such as those of 
potassium and sodium. The oxides of calcium, barium, stron- 
tium, magnesium, and aluminium are irreducible by carbon. 
The other oxides require for reduction a temperature more or 
less elevated, according to the force with which they reiain 
their oxygen. If the reduction be difficult, a high temperature 
is required, and carbon monoxide is formed ; otherwise carbon 
dioxide is the product. 

A small quantity of cupric oxide may be reduced by char- 




FiG. 93. 



coal by heating the mixture in a glass tube by the aid of a 
spirit-lamp (Fig. 93). Carbon dioxide is disengaged. 

2CuO + C == 2Cu -f CO^ 

Cupric oxide. Copper. 

But to reduce zinc oxide by charcoal, the mixture must be 



METALLIC OXIDES. 



243 



heated to bright redness in a clay or iron retort, and in this 
case carbon monoxide is evolved. 



ZnO + C 

Zinc oxide. 



Zn -I- CO 

Zinc. 



Chlorine decomposes nearly all of the oxides at a high tem- 
perature. It drives out the oxygen and combines with the 
metal, forming a chloride. Some of the oxides are irreducible 
by carbon, and resist also the action of chlorine. Such an 
oxide is aluminium oxide, or alumina. But if these oxides 
be submitted to the simultaneous action of chlorine and carbon 
at a high temperature, they are converted into chlorides, and 
carbon monoxide is disengaged. 

An intimate mixture of alumina and charcoal may be intro- 
duced into a porcelain tube, BB (Fig. 94), which is heated to 




Fig. 94. 

bright redness, and a current of dry chlorine then passed 
through. In this case, carbon monoxide is disengaged, while 
aluminium chloride is formed and volatilizes and may be con- 
densed in a cooled receiver. 

Sulplmr decomposes all of the oxides except alumina and its 
analogues. The reaction takes place at a high temperature, 
and gives rise to the formation of a sulphide and sulphurous 
oxide, or a sulphide and a sulphate if the latter be not decom- 
posable by heat. 



244 ELEMENTS OF MODERN CHE3IISTRY. 

If sulphur be heated with cupric oxide, cupric sulphide is 
formed and sulphurous oxide is evolved. 

2CuO -}- 3S = 2CuS + SO'^ 

Cupric oxide. Cupric sulpliiJe. 

However, if calcium oxide (lime) or lead oxide, PbO, be 
heated with sulphur, a sulphate and a sulphide are formed. 

4CaO -f- 2S^ = 3CaS + CaSO* 

Calcium oxide. Calcium sulphide. Calcium sulphate. 

Action of Water upon the Oxides — Metallic Hydrates 
and Acids. — If some fragments of barium oxide (baryta) be 
sprinkled with cold water, an energetic reaction immediately 
takes place. The water unites with the metallic oxide with so 
much energy that the heat disengaged is sufficient to convert 
a portion of the water into vapor. The barium oxide is con- 
verted into hydrate. 

BaO + WO ^ Ba(0H)2 

Barium oxide. Barium hydrate. 

In the same manner, the oxides of potassium and sodium 
energetically absorb the elements of water, being converted 
into hydrates. 

K^O + WO = 2K0H 

Potassium oxide. Potassium hydrate. 

The hydrates of potassium and sodium are soluble in water 
and their solutions are caustic, changing tincture of violet to 
a green color and restoring the blue color to reddened litmus 
solution. These hydrates constitute the alkalies. 

The hydrates of barium, strontium, and calcium are likewise 
soluble in water to a certain extent, and their solutions are also 
somewhat caustic. 

Other hydrates are insoluble ; they may be obtained by double 
decomposition by precipitating the corresponding salts with an 
alkali. 

If a solution of potassium hydrate be poured into a solution 
of cupric sulphate, a light-blue precipitate of cupric hydrate is 
formed. 

CuSO* -f- 2K0H = K^SO* + Cu(OH)^ 

Cupric sulphate. Potassium hydrate. Potassium sulphate. Cupric hydrate. 

But if this precipitate be heated, even in the liquid in 
which it was formed, it changes brown, and is converted into 
oxide by losing its water. 

Cu(OH)^ — WO == CuO 



SULPHIDES. 245 

A great number of metallic hydrates undergo the same 
decomposition when they are heated. 

There are true metallic acids which contain the elements of 
an oxide plus the elements of water. Such are 

H^CrO* = CrO' + H^O 

Chromic acid. Chromium trioxide. 

H^MnO* == MnO^^ + H^O 

Mangauic acid. Manganese trioxide. 

As far as their constitution is concerned, these metallic acids 
may be compared to sulphuric acid. 

H^SO* = SO' + H^O 

They also resemble sulphuric acid in their chemical func- 
tions ; each contains two atoms of basic hydrogen, that is, two 
atoms of hydrogen which are replaceable by a metal. 



SULPHIDES. 

Sulphur has a great tendency to unite with the metals, and 
the union often takes place with a vivid evolution of heat. 
Copper-turnings and iron-filings burn in the vapor of sulphur. 
The phenomena which favor or determine, and those which 
accompany this combination, have already been indicated, and 
we have seen that the presence of a small quantity of water 
favors chemical union in a mixture of sulphur and iron-filings. 

Certain metals, such as aluminium, zinc, and gold, resist the 
action of sulphur even at high temperatures. 

In composition the sulphides are analogous to the oxides. 

The more important of the transformations which they may 
undergo are the following: 

Oxygen decomposes all of the sulphides at a temperature 
more or less elevated. 

Finely-divided potassium sulphide, obtained by calcining the 
sulphate with an excess of charcoal, is a black powder, but it 
becomes incandescent on contact with oxygen, and if thrown 
into the air it produces a shower of sparks. It is known as 
Gay-Lussac's pyrophorus. Its fine state of division favors the 
absorption of oxygen, and the latter converts it into sulphate. 
K^S -I- 0* ^ K^SO* 

Potassium sulpliide. Potassium sulphate. 

Dry oxygen acts in the same manner upon all the sulphides 
21* 



246 ELEMENTS OF MODERN CHEMISTRY. 

when the corresponding sulphates are stable at high tempera- 
tures. In the contrary case, sulphurous oxide is formed, and 
a residue of oxide or even of metal is obtained, if the oxide be 
decomposable by heat. 

If zinc sulphide be roasted, it is converted into zinc oxide, 
and sulphurous oxide is evolved ; but if sulphide of mercury 
be heated in a current of air, metallic mercury is obtained. 

HgS + 0^ — Hg + SO^ 

Mercuric sulphide. Mercury. 

Moist oxygen acts upon the sulphides more readily than the 
dry gas. It unites with them at ordinary temperatures, form- 
ing sulphates. 

FeS -f 0* = FeSO* 

Sulphide of iron. Ferrous sulphate. 

Chlorine attacks all of the sulphides, forming metallic chlo- 
rides and sulphur chloride, if the dry method be employed, or 
with deposition of sulphur if the reaction take place in presence 
of water. 

Water dissolves the alkaline sulphides as well as those of cal- 
cium, barium, and strontium ; the sulphides of the other metals 
are insoluble in water. 

Hydrogen sylj)hide combines with certain sulphides, convert- 
ing them into sidphydrates. The analogy will be noticed be- 
tween this reaction and that of water upon the oxides. 
K^S + H^S = 2KSH 

Potassium sulphide. Potassium sulphydrate. 

K^O -f H^O = 2K0H 

Potassium oxide. Potassium hydrate. 

CHLORIDES. 

Chlorine, bromine, and iodine form with the metals com- 
pounds which possess the appearance and certain properties of 
salts. Indeed, common salt, or sodium chloride, has given the 
name to the entire class of saline compounds. Hence Berze- 
lius named chlorine, bromine, and iodine the halogen bodies, 
and called their combinations with the metals the haloid salts. 
Thus he admitted the relation between these compounds and 
the true salts, while at the same time distinguishing them by a 
particular name, for while they resemble the salts in their prop- 
erties, they differ from them in composition. This subject will 
be more fully considered farther on. 



CHLORIDES. 



247 



Composition. — All of the metals, with the exception of plat- 
inum, combine directly with free chlorine, but all do not com- 
bine with it in the same atomic proportions, and often the same 
metal forms several distinct combinations with this element. 
Hence the differences in the composition of the chlorides. 
They are formed by the union of an atom of metal with one, 
two, three, four, five, or six atoms of chlorine. 



KCl 


CaCP 


SbCP 


SnCP 


SbCP 


MoCP 


Potassium 


Calcium 


Antimony 


Tin 


Antimony 


Molybdenum 


chloride. 


chloride. 


trichloride. 


tetrachloride. 


pentachloride. 


hexachloride. 


NaCl 


FeCP 


BiCP 


TiCP 






Sodium 


Ferrous 


Bismuth 


Titanium 






chloride. 


chloride. 


trichloride. 


tetraciiloride. 






AgCl 


ZnCP 


AuCP 


PtCP 






Silver 


Zinc 


Gold 


Platinum 







chloride. chloride, trichloride, tetrachloride. 



To these chlorides must be added those which are formed 
by the union of two atoms of metal with two or six atoms of 
chlorine. 



Cu^CP 

Cuprous chloride. 

Hg^CP 

Mercurous chloride. 



APCP 

Aluminium chloride. 

Cr^CP 

Chromic chloride. 

Fe^CP 

Ferric chloride. 



Cuprous chloride and mercurous chloride contain for the 
same quantity of chlorine twice as much metal as cupric chlo- 
ride, CuCP, and mercuric chloride, HgCP. 

In the first, two atoms of copper or mercury are combined 
together to fix two atoms of chlorine, and these two atoms of 
metal remain thus associated in all the cuprous and mercurous 
compounds. It is the same in the chloride of aluminium, and 
in chromic and ferric chlorides. Each of them contains two 
atoms of metal intimately associated, and combined as a whole 
with six atoms of chlorine. 

The same metal may form several combinations with chlorine. 

Thallium combines with one or three atoms of chlorine. 

Tin and platinum combine with two or four atoms of chlorine. 

Antimony combines with three or five atoms of chlorine. 

Physical Properties of the Chlorides. — Most of the chlo- 
rides are solid and possess the aspect, color, and physical prop- 
erties of the salts of the same metal. Nearly all are crystalline 
and soluble in water. Only the chloride of silver, mercurous 



248 ELEMENTS OP MODERN CHEMISTRY. 

and cuprous chlorides are insoluble ; plumbic chloride and thal- 
lous chloride are but slightly soluble in water. 

Certain metallic chlorides are liquid at ordinary tempera- 
tures. Such are the tetrachlorides of tin and titanium. Some, 
like the chlorides of zinc and bismuth, are solid, but fusible at 
low temperatures. These latter were formerly designated as 
metallic butters. 

Most of the chlorides are fusible at high temperatures, and 
many of them are volatile and can be distilled without altera- 
tion. It is thus with the liquid chlorides, with the chlorides 
of zinc, bismuth, mercury, etc. 

Chemical Properties. — As a rule, the chlorides are very 
stable. Only the chlorides of certain of the precious metals, 
as those of gold and platinum, are entirely decomposed by a 
high temperature. Some of the higher chlorides lose chlorine 
when calcined, and are converted into lower chlorides. Thus, 
cupric chloride is converted into cuprous chloride when heated 
out of contact with, air. 

A great number of the chlorides are reduced when they are 
heated in a current of hydrogen. In this case, hydrochloric 
acid is disengaged, and the metal remains. Thus, hydrogen 
removes the chlorine from the chlorides of silver and iron. 
These decompositions are determined by the powerful affinity 
of chlorine for hydrogen. 

The action of the metals upon the chlorides gives rise to 
interesting phenomena which are worthy of study. 

If corrosive sublimate, which is mercuric chloride, be mixed 
with powdered tin and the mixture be heated in a small glass 
retort provided with a receiver, a liquid will soon collect in the 
latter which diffuses thick vapors in the air. It is the tetra- 
chloride of tin, called by the ancient chemists " fuming liquor 
of Libavius." It is formed by the decomposition of the mer- 
curic chloride, which gives its chlorine to the tin, metallic 
mercury being at the same time set free. 

Bismuth decomposes mercuric chloride in the same manner 
when the two substances are heated together. These experi- 
ments are conducted in the dry way. They may be modified 
by operating in the presence of water, in which we have re- 
marked that most of the chlorides are soluble ; it is thus with 
mercuric chloride. 

If a plate of copper be plunged into a solution of this body, 
it at once becomes covered with a layer of metallic mercury. 



CHLORIDES. 249 

That metal is displaced from its combination by the copper, 
which combines with the chlorine: cupric chloride is formed, 
and after the lapse of some time, the liquid will contain only 
that compound. It becomes green, and if a plate of zinc be 
plunged into it, the copper will be precipitated in its turn, and 
the zinc will combine with the chlorine and enter the solution ; 
the liquid then contains zinc chloride. 

Thus, the metals reciprocally displace each other from their 
solutions, according to the energy of their affinities. In this 
case it is the possession of the chlorine for which they antago- 
nize each other, the stronger driving out the weaker. It must 
be remarked that in this respect the chlorides behave in the 
same manner as the oxygen salts. 

This analogy is continued in innumerable reactions. Solu- 
tions of the chlorides enter into double decompositions like 
solutions of the true salts. If potassium hydrate be added to 
a solution of either cupric sulphate or cupric chloride, in each 
case a light-blue precipitate of cupric hydrate is obtained. 

CuSO* + 2K0H = K^SO* + CuCOH)^ 

Cupric sulphate. Potassium hydrate. Potassium sulphate. Cupric liydrate. 

CuCP -f 2K0H = 2KC1 + Cu(0H)2 

Cupric chloride. Potassium chloride. 

But cupric chloride resembles the sulphate in still another 
property. When perfectly pure it is yellowish. If it be moist- 
ened with water, it becomes heated and assumes a green color. 
It has combined with water, and will dissolve if enough of that 
liquid be added. A green liquor is thus obtained, which de- 
posits, by spontaneous evaporation, magnificent green prisms. 
These crystals are hydrated cupric chloride. They contain 
water of crystallization, and can only exist on that condition. 
It is the same with the crystals of cupric sulphate. 

Thus, certain chlorides are capable of taking water of crys- 
tallization like the true salts. 

We may complete the analogy by one more characteristic. 

1. If a solution of aluminium sulphate be added to a con- 
centrated solution of potassium sulphate, and the mixture be 
agitated, an abundant crystalline deposit is obtained. This is 
a double salt, — potassium and aluminium sulphate, or alum. 

2. If a solution of platinic chloride be added to a concen- 
trated solution of potassium chloride, a yellow precipitate is 



250 ELEMENTS OF MODERN CHEMISTRY. 

formed at once. It is the double chloride of potassium and 
platinum, which contains all of the elements of two molecules 
of potassium chloride and one molecule of platinic chloride. 
This example shows that the chlorides can combine together, 
forming double chlorides, just as the true salts may combine 
together to form double salts. 



SALTS. 

Definition. — The salts are formed by the substitution of 
metal for the hydrogen of the acids, and they result from the 
action of the acids upon the metallic oxides or hydrates. The 
name acid applies to two classes of compounds: the first are 
formed by the union of hydrogen with a strongly electro-nega- 
tive element, such as chlorine or bromine ; these are the %- 
dracids. Such are hydrochloric acid, HCl, and hydrobromic 
acid, HBr. 

The acids of the other class are more complicated, contain- 
ing hydrogen united with a strongly electro-negative oxidized 
group, that is, a group of atoms formed by oxygen and another 
element; these are the oxacids. Such are nitric acid, HNO^, 
and sulphuric acid, H^SO*. 

These two classes of acids behave in the same manner in 
contact with bases, that is, with metallic oxides or hydrates. 

1. If hydrochloric acid be gradually added to a concentrated 
solution of potassium hydrate, the liquid becomes heated, 
and, as it is neutralized by the acid, a white crystalline de- 
posit separates and augments on cooling : it is potassium 
chloride. 

2. If sulphuric acid diluted with its volume of water be 
cautiously and gradually added to a concentrated solution of 
potassium hydrate, the liquid becomes heated, and, as it is 
neutralized by the acid, a white crystalline deposit separates 
and increases on cooling : it is potassium sulphate. 

The analogy between the two reactions is marked. In each 
case a powerful base, potassium hydrate, has been neutralized 
by an energetic acid ; the reaction has been accompanied by 
the production of heat, and has given rise to the formation 
of a saline matter which has been deposited. The part of the 
reaction which is invisible is the formation of water. This 
formation of water, which always accompanies the generation 



SALTS. 251 

of a salt in the ordinary manners, is expressed in the following 
equations : 

KOH + HCl = KCl + WO 

Potassiuni hydrate. Potassium chloride. 

2K0H + H^SO* = K^SO* -f- 2W0 

Potassium sulphate. 

These reactions, it will be seen, consist in an interchange of 
elements, a double decomposition. The hydrogen of the acid 
is exchanged for the metal of the potassium hydrate and by 
the exchange the potassium hydrate is converted into water, 
while the acid, that is, the salt of hydrogen, is converted into a 
salt of potassium. All hydrogen compounds capable of thus 
exchanging their hydrogen for an equivalent quantity of metal, 
fill the functions of acids, and these acids become salts when 
their hydrogen is thus replaced by a metal. It may then be 
seen what an important part hydrogen plays in the formation 
of salts. From whence comes this property, this capacity for 
such exchanges, and of replacement by metals ? Without 
doubt from the element or group with which the hydrogen is 
united in the acids ; and in this respect chlorine and sulphur 
play the same parts in hydrochloric and sulphydric acids that 
the oxidized groups play in nitric, sulphuric, and phosphoric 
acids. 

HCl H^S 

Hydrochloric acid. Sulphydric acid. 

H(NO^) H\SO=^) WiVO') 

Nitric acid. Sulphurous acid. Phosphorous acid. 

H(ClO0 ff(SO*) H\PO*) 

Chloric acid. Sulphuric acid. Phosphoric acid. 

This property is characterized by saying that the elements or 
groups, to which the hydrogen is united, are strongly electro- 
negative, or acid, in opposition to the hydrogen, which is 
strongly electro-positive, or haste. 

When such an acid reacts upon an oxide, or upon a hydrate, 
an interchange of elements takes place, and a salt and water 
are formed ; the latter is a constant product necessary to the 
reaction. Other examples may be added to those already given. 

If a current of hydrogen sulphide be passed into a solution 
of potassium hydrate until no more is absorbed, potassium 
sulphydrate and water are formed. 

H^S + KOH = KSH -f- WO 

Potassium sulphydrate. 



252 ELEMENTS OF MODERN CHEMISTRY. 

If an excess of dilute sulpliuric acid be poured into a solu- 
tion of potassium hydrate, potassium acid sulphate and water 
are formed. 

H^SO* + KOII =^ KHSO* + H^O 

Potassium acid sulphate. 

Lastly, if cupric oxide be heated with dilute sulphuric acid, 
it dissolves, coloring the liquid blue. Cupric sulphate and 
water are formed. 

IPSO* -f Cuo = Cuso* f ir^o 

Cupric oxido. Cuprio 6nli)liate. 

Neutral, Acid, and Basic Salts. — If the salts result from 
the substitution of the metals for the basic hydrogen of acids, 
it is evident that their composition must be related to that of 
the acids from which they are derived. We know that the 
latter contain one, two, or three atoms of hydrogen, capable of 
being replaced by an equivalent quantity of metal : they are 
monobasic, dibasic, and tribasic. It is evident that the salts 
must present analogous differences in their composition, accord- 
ing as they are derived from a monobasic, a dibasic, or a tribasic 
acid. 

A salt is neutral when the basic hydrogen has been entirely 
replaced by an equivalent quantity of metal. But the substi- 
tution may be only })artial, for when an acid contains two atoms 
of basic hydrogen, only one of these atoms may be replaced by 
one atom of metal ; there will then remain in the salt thus 
formed one atom of basic hydrogen. 

When an acid contains three atoms of basic hydrogen, it 
may liappen that only one is replaced by one atom of nietal ; 
there will then remain in the salt two atoms of basic hydrogen ; 
or it may be that two atoms of hydrogen are replaced by an 
equivalent quantity of metal, and there will then remain in the 
salt a single atom of basic hydrogen. 

Whenever basic hydrogen thus remains in a salt, the satura- 
tion of the acid is said to be incomplete. The salt formed 
ordinarily retains the characters of an acid; it is an acid naif. 
The following table indicates the possible cases of complete 
or incomplete saturation which may be presented by a mono- 
basic, a dibasic, and a tribasic acid : 

IINO^' H^SO* UTO* 

Nitric acid. Sulphuric acid. Phosphoric acid. 



SALTS. 253 

KNO^ g| SO* ^2 [ PO* 

Potassium nitrate. Potassium acid sulphate. Monopotassium phosphate. 

Potassium sulphate. Dipotassiiim phospliate. 

Tripotassiiim phosphate. 

Certain neutral salts possess tlie property of combining with 
the hydrates or the oxides. The compounds so formed contain 
all of the elements of the neutral salt, plus those of the hydrate 
or oxide ; they are called basic salts. Thus, the oxides of 
lead and copper may combine with the various salts of lead and 
copper, forming basic salts of those metals. 

Richter's Laws. — Towards the close of the last century 
fruitful investigation was made into the phenomena of neu- 
tralization or saturation of acids by bases. We know that a 
given weight of acid requires for its neutralization a fixed and 
absolutely invariable quantity of a given base. Thus, for the 
conversion of 1000 grammes of sulphuric acid into neutral 
potassium salt, a quantity of potassium hydrate corresponding 
to 961 grammes of potassium oxide, K'^O, is required. To 
saturate these 1000 grammes of sulphuric acid, it is necessary 
to take weights of the oxides which are invariable for each one 
separately, but which vary among themselves. 

Thus, 1000 grammes of concentrated sulphuric acid are neu- 
tralized by the following quantities of the oxides named : 

Potassium oxide 961 grammes. 

Sodium oxide 632 " 

Barium oxide 1561 " 

Calcium oxide 571 " 

Zinc oxide 866 " 

Cupric oxide 811 " 

Mercuric oxide 2204 " 

Silver oxide 2367 " 

Again, to neutralize 1000 grammes of the most concentrated 
nitric acid, the following quantities of the same oxides are 
required : 

Potassium oxide 747 grammes. 

Sodium oxide 492 

Barium oxide ". . 1214 

Calcium oxide 444 

Zinc oxide 651 

Cupric oxide 631 

Mercuric oxide 1714 

Silver oxide 1841 

22 



254 ELEMENTS OF MODERN CHEMISTRY. 

Richter was the first to remark that these latter quantities 
are precisely in the same ratio to each other as the quantities 
of oxides which neutralize 1000 grammes of sulphuric acid. 
Thus, 

961^747 
632 492 
961 _ 747 

961 _ 147^ etc. 
571 444 

In other words, the quantities of oxides which neutralize a 
given weight of one acid are 'pro'portional to the quantities of 
the same oxides which neutralize the same weight of another 
acid. This law of the composition of salts was discovered, 
towards the close of the last century, by Richter, a chemist of 
Berlin. Berzelius quoted another German chemist, Wenzel, 
as the author of this law of proportion, and his error has 
appeared in all of the treatises on chemistry during the last 
fifty years. 

Richter also studied the phenomenon of the precipitation of 
metallic solutions by the metals. It is known that when a 
piece of iron is plunged into a solution of cupric sulphate, the 
iron dissolves, displacing a certain quantity of copper, without 
other change. Since the new salt formed, ferrous sulphate, ex- 
ists in the solution in the same conditions of neutrality as the 
cupric sulphate, the quantities of metal which thus displace 
each other are equivalent. As neither oxygen nor acid is set 
at liberty, it must be admitted that the respective quantities of 
the metals, in the salts successively formed, are united to the 
same quantity of oxygen. It has even been supposed that in 
the salts which, like the sulphates, contain four atoms of oxygen, 
the metal is in intimate relation with one of these atoms, which 
is precisely sufficient to constitute the metal in the state of 
monoxide. 

CuSO* = CuO,SO^ 
FeSO* = FeO,SO' 

If this were so, it is evident that when cupric sulphate is 
decomposed by iron, the quantity of metal which enters into 
solution would combine or enter into relations with precisely the 
quantity of oxygen abandoned by the copper. This quantity of 
oxygen being constant, the quantities of the metals which com- 



SALTS. 255 

bine successively with it, diiFer, but are equivalent to each 
other, and it is evident that the oxides thus formed would be 
more rich in oxygen as the weight of metal which enters into 
solution is less considerable; in other words, the richness of all 
these oxides in oxygen is inversely proportional to the weights 
of the metals which successively become dissolved ; it was in 
this form that Richter announced the second law of the com- 
position of salts. It will be seen that this law is implied in 
the jfirst, and that both are but particular cases and natural con- 
sequences of the theory of equivalents, as it is understood at 
present and as it has already been explained (page 23). 

General Properties of Salts. — The salts present very differ- 
ent colors. Those which are formed by an acid possessing a 
color are themselves colored ; such are the chromates, manga- 
nates, and permanganates. 

Most of the colored oxides form salts presenting various 
colors. 

Ferrous salts are bluish-green. 

Ferric salts are yellow or yellowish-brown. 

Manganese salts are rose-colored. 

Chromium salts are dark green. 

Nickel salts are green. 

Cobalt salts are currant-red or blue. 

Cupric salts are blue or green. 

Gold salts are yellow. 

It is to be remarked that these various colors are only devel- 
oped, as a rule, when the salts are hydrated, that is, combined 
with water of crystallization. The taste of the salts depends 
upon their solubility ; it is wanting altogether or but slightly 
marked in the insoluble salts ; more or less pronounced and 
very diverse in the soluble salts. The salts of magnesium are 
bitter ; the aluminium salts are astringent ; those of iron astrin- 
gent, with a metallic after-taste ; the salts of lead are at the 
same time sweet and astringent ; the salts of copper, antimony, 
and mercury have an acrid metallic taste, which is nauseous, 
and is called styptic. 

The salts generally present regular forms, more frequently 
occurring in crystals. Some of them are obtained as amor- 
phous precipitates, but in nature even these may assume the 
crystalline state. 

Isomorphism. — Certain salts which possess similar atomic 
compositions crystallize in identical or nearly identical forms; 
they are called isomorphous. It is thus with the double sul- 



256 ELEMENTS OP MODERN CHEMISTRY. 

phates, which are called alums, and of which ordinary alum 
or aluminium and potassium sulphate is the type. These alums 
are formed by the union of a sulphate, K^SO*)'^, with a sul- 
phate, M'-^SO^, and they all contain 24 molecules of water of 
crystallization. 

Thus, ordinary alum, 

AP_(SO^)^K^SO* 4- 24.WO 

Alumiaiuiu aud potassium double sulphate. 

is isomorphous with chrome alum and iron alum. 

Cr'^(SO^)lK^SO* + 24ffO 

Chromium and potassium double sulphate. 

Fe^CSO^jlK-^SO^ + 24^-^0 

Irou and potassium double sulphate. 

All of these alums crystallize in regular octahedra. Further, 
a solution containing two alums, for example, aluminium and 
potassium sulphate and aluminium and ammonium sulphate, 
deposits on concentration crystals in which the two salts are 
mixed. Such is the character of isomorphous bodies ; crystal- 
lizing in the same form, they may mix together and replace 
each other in all proportions in the same crystal. Many exam- 
ples of isomorphism will be cited in the course of this work. 
It will now be sufficient to add that this idea of isomorphism 
has rendered valuable service to chemical theory by permitting 
the grouping together of bodies similar both in crystalline form 
and atomic constitution, and by furnishing in such cases useful 
indications for the determination of the atomic weights. It is 
evident that when two similar combinations, two sulphates, for 
example, are recognized to be isomorphous, it is necessary to 
represent their constitutions by analogous formulae, and the 
latter can only be possible under the condition that the atomic 
weights of the metals contained in these sulphates have known 
values. 

Action of Water upon the Salts. — If water be poured upon 
and agitated with powdered chalk, a white, cloudy liquid is 
obtained. The chalk is suspended in the water without being 
dissolved ; it is simply held up in the form of minute particles, 
and if the liquid be allowed to stand, the precipitate is de- 
posited, and clear water again appears above the deposit. 

However, if saltpetre, or potassium nitrate, be agitated with 
water, a colorless, transparent liquid is obtained. The saltpetre 
is dissolved in the water; it has disappeared as a solid body. 



SALTS. 257 

It is melted by the water, as is commonly said, and is uniformly 
diffused through the liquid. It has itself become liquid, and 
this is the phenomenon of solution. It is accompanied by a 
production of cold, that is, an absorption of heat ; for in assum- 
ing the liquid state and becoming diffused throughout the water, 
the saltpetre must absorb heat. 

If the introduction of powdered nitre into the solution be 
continued, the solid still disappears, but a time arrives when 
the salt introduced ceases to dissolve ; for water at a given tem- 
perature can only dissolve a fixed quantity of a salt, and when 
this limit is attained, the solvent force of the water upon the salt- 
petre is exhausted. The water is then said to be saturated with 
the salt, and any excess of the latter remains in the solid state. 

But if now the solution be heated, this excess is in its turn 
dissolved, for the solubility augments with the temperature, 
and as the latter is elevated, a larger quantity of the salt is dis- 
solved. When the liquid begins to boil, the temperature and 
the solubility of the salt have reached their extreme limit. 

If the boiling saturated solution be allowed to cool, it depos- 
its a large portion of the salt in the form of crystals. In this 
manner voluminous, colorless, and transparent prisms are ob- 
tained which fill the vessel, and which are surrounded by a 
solution of saltpetre, saturated at the temperature to which the 
liquid has been cooled. This liquid is called the mother- liquor 
of the crystals. It is thus that soluble salts are crystallized by 
cooling their hot saturated solutions. 

Grenerally the same facts are observed for other soluble salts. 
Their solubility increases with the temperature; there are, 
however, some exceptions to this rule. Sodium chloride is 
not more soluble in hot than in cold water, and gypsum, or 
calcium sulphate, is sensibly more soluble in cold than in hot 
water; for, while 500 parts of boiling water are requisite to 
dissolve one part of gypsum, only 460 parts of cold water are 
necessary to dissolve the same quantity. The maximum solu- 
bility of sodium sulphate is between 32 and 33°. 

Crystals of nitre may be obtained by another process. We 
may expose the cold saturated solution to the air at the ordi- 
nary temperature, or, better still, place it in a bell-jar over a 
vessel containing sulphuric acid. The water of the solution 
slowly disappears, and, as it is dissipated in vapor, a portion of 
the dissolved salt separates in the solid form. The crystals thus 
formed by spontaneous evaporation are generally very regular. 

22* 



258 ELEMENTS OF MODERN CHEMISTRY. 

But water exerts another and a different action upon the 
salts. 

Perfectly dry cupric sulphate, CuSO*, is a white powder. 
If water be poured upon it, it becomes blue and dissolves, com- 
municating to the liquid a blue color and notably raising its 
temperature. On evaporation, this liquid deposits crystals of 
blue vitriol, and if these be compared with the dry white pow- 
der with which we started, they will be found to differ from it 
by the water they contain. We have employed the anhydrous 
salt, and have hydrated it. In fact, the sulphate, CuSO*, has 
absorbed five molecules of water, with which it has combined, 
and this combination, like all others, has taken place with the 
production of heat. The water which is thus absorbed by cer- 
tain salts, and which combines with them in definite propor- 
tions, is necessary to the formation of their crystals ; it is called 
water of crystallization. 

It is not necessary to the constitution of the salts them- 
selves ; they can exist without it, and generally lose it when 
they are heated to a temperature more or less elevated, without 
undergoing any other decomposition. Certain salts abandon 
their water of crystallization with such facility that they give 
it up to the surrounding air when the latter is not saturated 
with moisture. They then become opaque and lose their 
forms, for crystals cease to exist when their water of crystalli- 
zation is disengaged. These salts become covered with a dry 
powder in the air and are called efflorescent salts. 

It is seen by the example just cited that the phenomenon 
of solution of salts in water, which depends upon a physical 
action, upon a change of state, is often complicated with a true 
combination of the salt with water, that is, a chemical action 
which disengages heat. The latter is generally more energetic 
than the physical action, and the difference between the two 
effects is then manifested by an elevation of temperature. 

But the physical phenomenon is produced alone when the 
salt which dissolves is incapable of combining with water of 
crystallization. A depression of temperature is then observed, 
as we have seen in the case of nitre, the crystals of which are 
anhydrous; but another example will more clearly illustrate 
this important phenomenon. 

If water be poured upon recently fused and powdered calcium 
chloride, the salt dissolves with production of heat. It changes 
not only its state but its composition ; it combines energetically 



SALTS. 259 

with the water, and this combination produces more heat than 
is absorbed by the change of state. Hence there is an eleva- 
tion of temperature. 

If calcium chloride, combined with its water of crystalliza- 
tion, be rapidly mixed with snow, the salt is so soluble in water 
that it causes the snow to melt at the same time that it becomes 
liquid itself. Here there is no combination, no chemical action, 
and no heat is disengaged. It is a double physical phenome- 
non, — fusion of the snow and fusion of the calcium chloride, — 
and neither of these bodies can undergo a change of state with- 
out absorbing heat. Hence there is a depression of tempera- 
ture which may reach — 40°. 

A mixture of snow and calcium chloride is a freezing mix- 
ture. A mixture of equal parts of common salt and broken 
ice or snow is frequently used for the production of cold. 

The phenomenon of the solution of salts in water presents 
none of the characteristics of a chemical action ; it does not 
take place in definite proportions. 

In fact, a soluble salt requires for its complete solution a 
quantity of water, which is always the same for a certain weight 
of the salt at a given temperature ; but there exists no atomic 
relation between this quantity of water and the weight of the 
salt which is dissolved. 

Further, although the solubility of a salt presents for each 
temperature a maximum limit, that is, although a given weight 
of a salt requires for its solution a quantity of water which is 
invariable and which cannot be diminished, when the solution 
has been accomplished an indefinite quantity of water may be 
added, and the liquid will still remain perfectly homogeneous. 

Supersaturation. — We have seen that a saturated solution 
of a salt at a given temperature generally deposits a part of 
that salt on cooling. This is not always the case ; it sometimes 
happens, if the cooling take place under certain conditions, that 
a portion of the salt, which the difference in temperature should 
reduce to the solid state, still remains in solution. The solu- 
tion is then said to be supersaturated. Sodium sulphate and 
alum have a great tendency to form such solutions. 

A hot, saturated solution of sodium sulphate is contained in 
the tube A (Fig. 95). It is heated to boiling, so that the vapor 
escapes by the drawn-out extremity. By the aid of a blow- 
pipe, the tube is then sealed at C, before the vapor can con- 
dense, and is then allowed to cool. A vacuum is formed above 



260 



ELEMENTS OF MODERN CHEMISTRY. 



the solution, for the air has been driven out by the vapor. The 
cold liquid remains limpid ; it deposits no crystals. But the 
instant the drawn-out point of the tube is broken off, the air 
enters and crystallization at once commences at the surface and 




Fig. 95. 

proceeds throughout the entire mass, which becomes solid ; at 
the same time an elevation of temperature may be observed. 

100 grammes of water and 200 grammes of crystallized so- 
dium sulphate may be heated to ebullition in a narrow-necked 
flask, and as soon as vapor begins to issue from the mouth, the 
latter may be covered with a watch-glass and the whole allowed 
to cool tranquilly. The salt remains dissolved, and the solution 
contained in the flask is supersaturated; but as soon as the 
watch-glass is removed the liquid becomes a solid mass of crys- 
tals (Loewel). 

In the first experiment it is the sudden entry of the air 
which determines the crystallization; in the second, it is the 
free access of air, and it may be admitted that in each case the 
air acts by the corpuscles which it holds in suspension, and 
which, fldling into the solution, determine the crystallization. 
Indeed, Loewel has shown that air which has been filtered 



SALTS. 261 

through cotton-wool has lost the property of causing supersat- 
urated solutions to crystallize. 

But what is the nature of these particles which by falling 
upon the surface of supersaturated solutions occasion crystalli- 
zation ? The researches of G-ernez have thrown great light upon 
this question. According to him, they are saline particles simi- 
lar to the salt dissolved. The sodium sulphate is deposited in 
the preceding experiments because the entry of the air has 
allowed an imperceptible particle of sodium sulphate to fall 
upon the surface of the liquid, and around this particle the 
crystallization begins immediately and is propagated through- 
out the entire mass of the supersaturated liquid. The air then 
contains a trace of sodium sulphate, as it contains a trace of 
common salt and of carbonate and sulphate of calcium. These 
particles are suspended in the air in a state of extreme division, 
and are carried from great distances by the winds. 

A boiling saturated solution of sodium hyposulphite may be 
allowed to cool in a carefully-corked flask. When cold, it is so 
concentrated that it possesses an oily consistency. The flask 
may be carefully uncorked and the surface of the liquid touched 
with a rod to the end of which a small particle of sodium hy- 
posulphite has been made to adhere. Crystallization at once 
commences at the spot where the rod touches the liquid, and 
in a few seconds the whole mass becomes solid. There is at 
the same time a notable disengagement of heat (Gernez). 

The crystallization will also take place if a particle of sodium 
sulphate be allowed to fall into the solution, for the latter salt 
possesses the same crystalline form as sodium hyposulphite, and 
an analogous constitution. 

Ebullition of Saline Solutions. — Aqueous solutions of the 
salts generally possess a boiling-point higher than that of water. 
Thus, a saturated solution of common salt boils at 108.4°; a 
saturated solution of potassium nitrate boils at 115.9°; and a 
saturated solution of calcium chloride boils only at 179.5°. 

Action of Heat upon the Salts. — The hydrated salts lose 
their water when they are heated. Ordinarily, a temperature 
of 100° is sufficient to expel the water of crystallization. Cer- 
tain salts melt in this water before losing it ; they are so soluble 
in hot water that they dissolve in the water which at a lower tem- 
perature constitutes them in the crystalline state. This is called 
aqueous fusion. A great number of anhydrous salts melt when 
they are exposed to intense heat ; this is called igneous fusion. 



262 



ELEMENTS OF MODERN CHEMISTRY. 



Heat exerts a decomposing action upon many salts. Upon 
this point it is difficult to give general laws. It can only be 
said that the stability of a salt depends upon three conditions, 
namely, the fixedness of the corresponding acid, the stability 
of the corresponding oxide, and the energy of the affinity with 
which the two react together to form the salt. 

Thus the salts of acids decomposable by heat are themselves 
decomposed at an elevated temperature. It is thus with the 
chlorates, the perchlorates, and the nitrates. Among the sul- 
phates, some are decomposable, others are fixed. The latter are 
those of potassium, sodium, barium, strontium, calcium, mag- 
nesium, lead, etc. The corresponding oxides of potassium, 
sodium, barium, etc., are fixed bases, and possess a powerful 
affinity for sulphuric acid. Hence their sulphates are stable. 

Most of the carbonates are decomposable by heat; indeed, 
the affinity of carbonic acid for the bases is as a rule feeble. 
It is exceptionally strong for the alkaline bases ; hence the alka- 
line carbonates and barium carbonate resist the action of heat. 
Action of Electricity upon the Salts. — When an electric 

current traverses the aque- 
ous solution of a salt, the 
latter is decomposed. The 
metal separates at the neg- 
ative pole, and the other 
element of the salt at the 
positive pole. This other 
element may be an elec- 
tro-negative element, such 
as chlorine, or an oxidized 
group, that is, a group of 
atoms, one or more of 
which is oxygen. 

The electrolysis of a 

salt may be effected as 

follows : An U tube ( Fig. ' 

96) contains a solution of 

cupric chloride. In each 

branch a plate of platinum 

dips into the liquid, and 

^iG- 96. these plates, connected by 

conducting wires with the two poles of a battery, constitute 

the positive and negative electrodes. 




As soon as the current 



SALTS. 263 

passes, the electro-positive element of the salt, the copper, is 
deposited upon the electro-negative electrode, and the chlorine, 
which is electro-negative, is disengaged at the positive electrode. 
A part of this chlorine combines with the platinum electrode 
by a secondary reaction, forming platinum chloride, but the 
principal action, that is, the decomposition of cupric chloride 
by electrolysis, is represented by the following equation : 

CuCP =: Cu -f ci^ 

Cupric chloride. Copper. Chlorine. 

If the cupric chloride be replaced by cupric sulphate, the 
current will decompose this salt into copper, which deposits 
upon the negative electrode, and into SO*, which possesses no 
stability, and consequently breaks up at the positive electrode 
into SO^ which combines with the water to form sulphuric 
acid, and 0, which is disengaged at the positive electrode. 

The decomposition of the SO* is a secondary action. The 
principal action accomplished by the work of the current is 
expressed by the following equation : 

CuSO* =: Cu + so* 

Cupric sulphate. Copper. Oxidized group. 

The secondary reactions are as follows : 
SO* = SO^ + o 
SO^' -f H^O = H^SO* 

The experiment may be repeated upon potassium sulphate, 
and a solution of this salt colored by the syrup of violets is in- 
troduced in the U tube. As soon as the current passes, bub- 
bles of gas are seen to arise from each electrode. Free oxygen 
appears at the positive electrode, as in the preceding case, and 
at the same time the liquid filling this branch of the tube as- 
sumes a red color. This is the evidence of the presence of 
sulphuric acid formed at the positive electrode. 

The gas disengaged at the negative electrode is hydrogen, 
which is produced by a secondary action of the water upon the 
potassium which is removed from the salt at the negative pole. 
Potassium hydrate is thus formed, and the syrup of violets 
in this branch of the tube is colored green. The principal ac- 
tion accomplished by the current is expressed, as in the pre- 
ceding cases, by the equation 

K'SO* = K' -f SO* 

Potiifssinm siilphato. Totassium. Oxidized group. 



264 ELEMENTS OF MODERN CHEMISTRY. 

The metal, which is electro-positive, is carried to the nega- 
tive pole ; the oxidized group to the positive pole. But the 
two elements thus separated have provoked or undergone sec- 
ondary actions independent of the work of the current. The 
potassium has decomposed the water, the oxidized group has 
been broken up, as explained in the preceding case. 

It will be understood from these reactions that all of the 
salts, whatever may be their nature, undergo the same kind of 
decomposition when submitted to the action of an electric cur- 
rent. They are separated into two elements. The one is elec- 
tro-positive, and is liberated at the negative pole ; this is always 
the metal. The other is electro-negative and goes to the posi- 
tive pole, whether it be a simple body, such as chlorine, or an 
oxidized group, such as SO*. It will also be seen that such 
groups occupy in the oxidized salts the same position held by 
chlorine in the chlorides. Such is the principal action, that is, 
the decomposition, accomplished by the action of the electric 
current, a decomposition which is called electrolysis. 

Action of the Metals upon the Salts. — The metals may 
displace each other in their saline solutions. 

If a plate of copper be plunged into a solution of silver 
nitrate, the copper enters into solution in the form of cupric 
nitrate, displacing and precipitating the silver. 

Cu 4- 2AgN0^ = Cu(NO^)^ + Ag^ , 

Silver nitrate. Cupric nitrate. 

If a piece of iron be introduced into a solution of cupric 
sulphate, the iron instantly becomes covered with a layer of 
metallic copper, precipitated by a portion of the iron which 
enters the solution. 

Fe -f CuSO* = Cu + FeSO* 

Cupric sulphate. Ferrous sulphate. 

If a strip of zinc around which some brass wires have been 
twisted be suspended in a dilute solution of plumbic acetate, 
the zinc will slowly displace the lead, which will be deposited 
in brilliant scales upon the brass wires. The latter gradually 
assume the appearance of fern-leaves, and the experiment 
constitutes the formation of the lead-tree. 

Richter, of Berlin, was the first to remark (1792) that the 
metals displace each other in their saline solutions without the 
neutrality of the latter being disturbed. When a neutral salt 
is precipitated by a metal, a new neutral salt results. The 



BERTHOLLET S LAWS. 



265 



ferrous sulphate formed by the action of iron upon cupric sul- 
phate is neutral like the latter. 

It may be further stated that in this respect the chlorides 
behave like the oxygen salts. Iron displaces copper from cu- 
pric chloride as from the sulphate. In the first case it com- 
bines with CP, in the second with SO*, and in this circumstance 
again the latter group acts in the same manner as chlorine. 



Cu 



Cu 



CuCP . + Fe = FeCP + 

Cupric chloride. Ferrous chloride. 

Cu(SO*) 4- Fe == Fe(SO*) + 

Cupric sulphate. Ferrous sulpliate. 

The following table indicates the order in which the metals 
precipitate saline solutions : 



SALTS OF WHICH THE METALS ARE PRECIPITATED BY 
CERTAIN METALS. 



Salts of tin . . 
Salts of antimony 
Salts of bismuth 
Salts of lead 
Salts of copper . 

Salts of mercury 



Salts of silver . 
Salts of platinum 
Salts of gold . . 



reduced by iron, zinc, 
and all the preceding 

metals 

f reduced by iron, zinc, 
J manganese, cobalt, 
) and all the preceding 
[ metals 



reduced by iron and zinc. 



BERTHOLLET'S LAWS. 

To conclude this general study of the salts, it only remains 
to indicate the actions exerted upon them by the acids and the 
bases, and the reciprocal actions of the salts themselves. These 
facts have been established and discussed principally by Ber- 
thollet, who demonstrated the influence of physical conditions, 
such as insolubility and volatility, upon the direction of chem- 
ical decompositions. 

Action of Acids upon the Salts. — When an acid, that is, a 
salt of hydrogen, is added to a metallic salt, the former tends 
to exchange elements with the latter, in such a manner as to 
form a new salt and a new acid. 

If sulphuric acid be added to powdered potassium nitrate, 
M 23 



266 ELEMENTS OF MODERN CHEMISTRY. 

the latter partially dissolves without the aid of heat, and 
potassium acid sulphate and nitric acid are formed. 

KNO^ + H^SO* = HNO=^ + KHSO* 

Potassin Ml nitrate. Sulphuric acid. Nitric acid. Potassium acid sulphate. 

But this reaction is by no means complete. Powerful as 
are its affinities, the sulphuric acid cannot decompose the whole 
of the potassium nitrate unaided by heat ; a portion of the latter 
salt remains unaltered in presence of the excess of sulphuric 
acid, so that the resulting thick and fuming liquid really con- 
tains two acids and two salts, namely : 

Sulphuric acid. 
Nitric acid. 

Potassium acid sulphate. 
Potassium niti'ate. 

The reaction takes place as if two acids were in presence of 
a single base. There is a conflict between the acids, and they 
tend to divide the base, which is potassium, in such a manner 
that each acid may saturate a portion. 

Hence the decomposition of potassium nitrate is not com- 
plete, and it is arrested as soon as the nitric acid set free can 
dispute with the sulphuric acid the possession of the base. 
There is then established a state of equilibrium between the 
two acids, both remaining in presence of the two salts. 

But this equilibrium is unstable and may be deranged by 
various circumstances. 

If the acid mixture be heated, abundant white vapors are 
disengaged. It is the nitric acid which volatilizes. But the 
sulphuric acid becomes thus preponderant in the liquid and 
decomposes another portion of potassium nitrate, and, if the 
volatilization of the nitric acid set free be not arrested by the 
removal of the heat, it is evident that nothing can prevent the 
complete decomposition of the potassium nitrate by the sul- 
phuric acid. The nitric acid, which by its presence alone 
prevented this total decomposition, is rendered powerless. 

Such is the influence of volatility or the gaseous state upon 
the progress of decompositions ; it is manifested in the highest 
degree in acids more volatile than nitric acid, such as carbonic 
and sulphurous acids. We have already seen that the carbon- 
ates and sulphites are easily and entirely decomposed by. the 
energetic acids. 

AVhile the volatility of acids favors the decomposition of 
their salts, insolubility may play an analogous part. 



berthollet's laws. 267 

If hydrochloric acid be added to a solution of potassium sili- 
cate, a gelatinous precipitate of silicic acid is at once produced, 
and at the same time potassium chloride is formed. The de- 
composition is complete, for the silicic acid is insoluble. 

If sulphuric acid be poured into a solution of barium nitrate, 
a precipitate of barium sulphate is immediately formed, while 
at the same time nitric acid is set free. 

Ba(N0^)2 -f ffSO* = 2HN0^ + BaSO* 

Barium nitrate. Sulphuric acid. Nitric acid. Barium sulphate. 

In this case also the decomposition is complete, for the ba- 
rium sulphate is insoluble. 

In these two reactions, the division of the base between the 
two acids cannot take place, &ince one of the products is imme- 
diately removed from the sphere of action by its insolubility. 
In the first case, it is the newly-formed acid which is precipi- 
tated ; in the second, it is the newly-formed salt which is de- 
posited in the insoluble state. 

Influence of Mass. — One other circumstance can influence 
the extent of these decompositions : it is the relative masses of 
the bodies which are in presence of each other. 

In the first experiment, it was supposed that an amount of 
sulphuric acid had been added to potassium nitrate sufficient to 
produce the double decomposition. If a large excess had been 
employed, it is evident that it would have become preponderant 
in the mixture, and that it would have displaced a more con- 
siderable portion of nitric acid. 

The influence of mass is manifested in the case of very feeble 
acids, and permits them to displace stronger acids. If a small 
quantity of tricalcic phosphate be introduced into water charged 
with carbonic acid, the latter, compensating by its mass for its 
deficiency in energy, will remove from the phosphate a portion 
of its base. Calcium dicarbonate and calcium acid phosphate 
are formed, both of which are soluble. 

Such, according to Berthollet, is the influence of insolubility 
and volatility upon the phenomena of double decomposition ; 
such, on the other hand, is the influence of mass. The same 
conditions intervene, and in the same manner, in the reactions 
which we are about to study. 

Action of Bases upon the Salts. — We will here consider 
only the action of the soluble bases, that is, the alkaline hy- 
drates. 



268 ELEMENTS OP MODERN CHEMISTRY. 

If a solution of potassium hydrate be poured into a solu- 
tion of sodium sulphate, no apparent change takes place ; but, 
according to the principle which has just been announced, it is 
probable that the potassium hydrate has liberated a portion 
of sodium hydrate. 

Na^SO* + 2K0H = K^SO* + 2NaOH 

Sodium sulphate. Potassium hydrate. Potas-iium sulphate. Sodium hydrate. 

But this decomposition cannot be complete, and the liquid 
must contain four bodies, namely : 

Sodium sulphate. 
Potassium sulphate. 
Sodium hydrate. 
Potassium hydrate. 

If potassium hydrate be added to a solution of cupric sul- 
phate, a light-blue precipitate of cupric hydrate is obtained. 
In this case the decomposition is complete, owing to the insol- 
ubility of the cupric hydrate which cannot dispute with the 
potassium hydrate the possession of the acid. 

CuSO* + 2K0H = K^SO* + Cu(OH)^ 

Cupric sulphate. Potassium hydrate. Potassium sulphate. Cupric hydrate. 

If a solution of barium hydrate be poured into a solution of 
potassium sulphate, a precipitate of barium sulphate is pro- 
duced, and potassium hydrate remains in solution. In this 
case again, the decomposition is complete, by reason of the in- 
solubility of the barium sulphate. The potassium cannot di- 
vide the acid with the barium, for the latter escapes with all 
of it in the form of insoluble sulphate. 

K^SO* + Ba(OH)^ = BaSO* + 2K0H 

Potasshim sulphate. Barium hydrate. Barium sulphate. Potassium hydrate. 

Action of the Salts upon each other. — The action of salts 
upon each other is what would naturally follow from the prin- 
ciples exposed in treating of the action of acids upon salts. 
Indeed, the latter possess the same constitution as the acids, 
and in their reactions upon salts should give rise to phenomena 
of the same order. These are exchanges of elements, double 
decompositions, which take place and are more or less complete, 
according to the physical conditions of the bodies which are 
produced, and also according to the relative masses of the re- 
acting bodies. 

In the first place, we must consider the reciprocal actions of 
the soluble salts. 



berthollet's laws. 269 

If a solution of cupric sulphate be treated with a solution 
of sodium chloride, no precipitate is formed, but the blue color 
of the liquid is changed to green. This color is that of cupric 
chloride, and it may be supposed that the latter salt is formed 
by the reciprocal action of the sodium chloride and cupric 
sulphate. 

CuSO* + 2NaCl = Na^SO^ + CuCP 

Cupric sulphate. Sodium chloride. Sodium sulphate. Cupric chloride. 

But this interchange of elements between the cupric sulphate 
and the sodium chloride is arrested before the decomposition 
of the two salts is complete. A part of each remains unaltered 
in the presence of the other and of the two new salts which 
are formed. Consequently, the green liquor obtained in this 
experiment contains four salts, namely : 

Cupric sulphate. 
Sodium chloride. 
Sodium sulphate. 
Cupric chloride. 

The respective proportions in which these salts exist in the 
mixture depend upon several circumstances. Malaguti has 
shown that in cases of this kind it is the energy of the affinity 
of the acids for the bases which governs the decomposition. 
The most energetic acid tends to combine with the most power- 
ful base, and the proportion of the salt thus formed predomi- 
nates in the mixture. Thus there is set up, as it were, between 
the elements in presence a sort of conflict, in which the stronger 
are victorious, while the weaker are not altogether annihilated. 
The result is a state of equilibrium which is only disturbed in 
case one of the products is by reason of its insolubility removed 
from the sphere of action of the other. The latter condition 
is realized in the following experiments. 

When barium chloride is added to the blue solution of cupric 
sulphate, a precipitate of barium sulphate is immediately formed, 
and cupric chloride remains in solution, coloring the liquid 
green. 

CuSO* + BaCP = BaSO* + CuCP 

Cupric sulphate. Barium chloride. Barium sulphate. Cupric chloride. 

In this case the decomposition is complete, owing to the in- 
solubility of the barium sulphate. That salt is removed by 
cohesion from the sphere of action of the compounds which 
remain in solution. The portions first formed, and thus with- 

23* 



270 ELEMENTS OF MODERN CHEMISTRY. 

drawn, are replaced by others, and the reaction once commenced 
is finished in the same manner, so that the whole of the cupric 
sulphate is converted into barium sulphate. 

A concentrated solution of common salt produces no precipi- 
tate in a concentrated solution of magnesium sulphate. How- 
ever, we must admit that there is an interchange of elements, 
and that the liquid contains four salts, namely : 

Magnesium sulphate. 
Sodium chloride. 
Sodium sulphate. 
Magnesium chloride. 

If this solution be exposed to an intense cold, it deposits 
crystals of sodium sulphate, while magnesium chloride remains 
in solution (Balard). Of the four salts which are in presence 
of each other, the sodium sulphate is the least soluble ; it is 
therefore deposited, and the double decomposition continues 
in the same manner until the greater part of the magnesium 
sulphate has been decomposed. 

The subject could be further developed by other examples. 
Those which have been given are sufficient to expose the true 
principle of double decomposition. 

We may add that if the operations be conducted in the dry 
way and at a high temperature, the volatility of the products 
which may be formed exerts an influence upon the reactions 
analogous to that which has been established for insolubility. 

If an intimate mixture of mercuric sulphate and sodium 
chloride be heated in a glass matrass, a sublimate of mercuric 
chloride is formed. 

HgSO^ + 2NaCl = Na^SO* + HgCP 

Mercuric sulphate. Sodium chloride. Sodium sulphate. Mercuric chloride. 

Action of Soluble Salts upon Insoluble Salts. — The study 
of double decomposition may be concluded by a summary ex- 
position of the action of soluble salts upon insoluble salts. It 
is analogous to that which has just been studied, that is, it is 
characterized by a tendency to an interchange of elements. A 
single example will be sufficient. 

If a solution of sodium carbonate be boiled for a long time 
with barium sulphate, it is found that the latter salt has under- 
gone a partial decomposition. It is partially converted into 
barium carbonate, insoluble like the sulphate, and the liquid 
becomes charged with a certain quantity of sodium sulphate. 
BaSO^ -f Na'^CO^^ = Na'^SO^ + BaCO^ 

Barium sulphate. Sodium carbonate. Sodium sulphate. Barium carbonate. 



NITRATES. 271 

This decomposition is more complete as the proportion of 
sodium carbonate which reacts upon the barium sulphate is 
increased. Here, as in some of the preceding experiments, the 
influence exerted by the greater mass is very appreciable. 

This study may be aptly terminated by summary indications 
upon the composition and properties of the more important 
classes of salts, which are the nitrates, sulphates, and carbonates. 

NITRATES. 

Composition. — Nitric acid containing HNO^ the nitrates 
contain the group NO' combined with a metal which replaces 
the hydrogen of the acid. Consequently they contain one or 
more groups, NO^, according to the nature of the metal which 
has neutralized the nitric acid. Thus, 



1. KOH -f 


HNO^ 


= KNO' + 


WO 


Potassium hydrate. 


Nitric acid. 


Potassium nitrate. 




2. PbO + 


2HN0^ 


= PbCNO')' + 


wo 


Plumbic oxide. 




Plumbic nitrate. 





3. hU^' + 3HN0' = Bi(NO=^)' + 3ffO 

Bismuthic liydrate. Bismuth trinitrate. 

With these few examples, we may conclude : 

1. That potassium, which unites with one atom of chlorine 
to form potassium chloride, KCl, unites also with one group, 
N0'\ to form potassium nitrate. 

2. That lead, which unites with two atoms of chlorine to 
form plumbic chloride, PbCP, unites also with two groups, 
NO'^, to form plumbic nitrate. 

3. That bismuth, which unites with three atoms of chlorine 
to form bismuth trichloride, BiCP, unites also with three groups, 
NO^, to form bismuth trinitrate. 

In the chloride K'Cl potassium is monatoraic. 

In the chloride Pb"C12 lead is diatomic. 

In the chloride Bi"'Cl3 bismuth is triatomic. 

In the nitrates, these three metals play the same parts as in 
the chlorides ; and we may say, in a general manner, that the 
metallic nitrates contain a metal united with as many times 
NO' as the metal possesses atomicities. 

In K'(NO^) monatomic potassium is united with NO^ 

In Pb"(N03)2 diatomic lead is united to 2N03 

In Bi"'(N0'^)3 triatomic bismuth is united to SNO^ 

Such is the law of the composition of the nitrates. 



272 ELEMENTS OF MODERN CHEMISTRY. 

Properties. — All of the nitrates are soluble in water. Some 
of them are deposited from their solutions in the form of hy- 
drated crystals. Such is cupric nitrate, which crystallizes with 
six molecules of water at a low temperature. 

Others separate in anhydrous crystals. Such are the nitrates 
of potassium, sodium, silver, barium, and lead. 

All of the nitrates are decomposable by heat, and the pro- 
ducts of the decomposition vary with the nature of the nitrate 
and with the temperature. Thus, potassium nitrate is first 
converted into nitrite, and this is finally decomposed into 
nitrogen, oxygen, and potassium oxide. The nitrates of barium 
and lead yield nitrogen peroxide, oxygen, and a residue of 
oxide. Silver nitrate yields nitrogen peroxide, oxygen, and a 
residue of metal. 

2AgN0' = N'^0* + 0' + Ag^ 

All of the nitrates liberate oxygen when they are heated; 
rich in oxygen, they constitute an abundant source of that 
element, and they are also easily reduced by bodies possessing 
a strong affinity for it. 

Sulphur, charcoal, phosphorus, and certain metals are ener- 
getically oxidized when heated with the nitrates. 

If sulphur be heated with potassium nitrate, potassium 
sulphate is formed, and sulphurous oxide and nitrogen are 
disengaged. 

2KN0^ + S^ = K^SO* + SO^ + N^ 

Potassium nitrate. Potassium sulphate. 

When powdered potassium nitrate is thrown upon burning 
charcoal, the salt melts and increases the combustion of the 
charcoal, producing a vivid deflagration. Potassium carbonate 
is formed and carbon dioxide and nitrogen are disengaged. 

4KN0^ + 50=. 2K2CO^ + 3C0^ + 2K\ 

Potassium nitrate. Potassium carbonate. 

Distinctive Characters. — All of the nitrates deflagrate when 
thrown upon incandescent charcoal. 

With concentrated sulphuric acid they evolve white vapors of 
nitric acid in the cold, and more abundantly when the reaction 
is aided by heat. When mixed with copper-filings and treated 
with concentrated sulpliuric acid, they disengage red vapors. 

When the solution of a nitrate is mixed with its own volume 
of concentrated sulphuric acid, and a. crystal of ferrous sulphate 
is introduced into the liquid, the crystal very soon assumes a 



SULPHATES. 273 

brown color which is communicated to the liquid. In this 
very delicate reaction the nitric acid is reduced by the ferrous 
sulphate to nitrogen dioxide, which colors the excess of ferrous 
sulphate brown (page 154). 

The solution of a nitrate, when treated with sulphuric acid, 
will decolorize solution of sulphate of indigo when the liquid 
is heated to boiling. 

SULPHATES. 

Composition. — Sulphuric acid, H^SO*, contains two atoms 
of hydrogen capable of being replaced by a metal. When both 
are replaced by an equivalent quantity of metal, a neutral sul- 
phate is formed. An acid sulphate is formed when a single 
one of these atoms of hydrogen is replaced by a single atom of 
metal. The hydrogen of the acid is removed by the oxygen 
of the metallic oxide or hydrate which more or less completely 
saturates the sulphuric acid. Several cases may be presented. 

1. K'OH 4- H^SO* = ^'\ SO* + H^O 



5! 



Potassium hydrate. Potassium acid sulphate. 

2. 2K'0H + H^SO* = K'^SO* + 2H=^0 

Potassium sulphate. 

3. Pb"0 + H^SO* =: Pb"SO* + H^O 

Plumbic oxide. Plumbic suljihate. 

r H^so* ( so* 

4. (AP)-O^ -f ] WSO' = (AP)" ] SO* + SH^O 

(h^so* (so* 

Aluminium oxide. '6 molecules. Aluminium sulphate. 

These examples show that all of the sulphates contain the 
group SO*, which in sulphuric acid is united with two atoms 
of hydrogen. This group is diatomic; it is necessary, then, 
that in the sulphates it shall be united with a quantity of metal 
equivalent to two atoms of hydrogen. 

1. In the acid sulphates it is united with an atom of hydro- 

gen and an atom of a monatomic metal, tt [ SO*. 

2. It is united with two atoms of a monatomic metal in the 
neutral sulphates R'^SO*. 

3. With one atom of a diatomic metal in the neutral sul- 
phates M"SO*. 

These cases are very simple. It is not so, however, with 



274 ELEMENTS OF MODERN CHEMISTRY. 

the fourth, in which we consider the saturation of sulphuric 
acid by an oxide R^O^, such as ferric oxide or aluminic oxide. 
Each of the three atoms of oxygen of the oxide R^O^ removes 
H^ from a molecule of H^SO*, and it results that the metal 
which was combined with 30", combines with 3(S0^)". The 
two atoms of metal which are substituted for 3H'^ in three mol- 
ecules of H'-SO* are then equivalent to 6 atoms of hydrogen. 
They are hexatomic, as is marked by the index ""K 

Properties. — The sulphates are nearly all soluble in water. 
Those of barium, strontium, and lead are insoluble. The sul- 
phates of calcium and silver, and mercurous sulphate are but 
slightly soluble. 

The alkaline sulphates, and those of calcium, barium, stron- 
tium, magnesium, and lead, are undecomposable by heat. The 
others are decomposed at a high temperature. A residue of 
oxide generally remains, while sulphurous oxide and oxygen 
are disengaged. The sulphates of zinc and copper are thus 
decomposed at a high red heat. 

CuSO* = SO^ + + CuO 

Cupric sulphate. Cupric oxide. 

In case the oxide is reducible by heat, the residue consists 
of metal. 

HgSO* := Hg + SO'^ + 0^ 

Mercuric sulphate. Mercury. 

The sulphates R^(SO*/ are decomposed at a comparatively 
low temperature, disengaging vapor of sulphur trioxide and 
leaving a residue of sesquioxide. 

Fe\'SO*/ = Fe^O^ + 3S0^ 

Ferric sulphate. Ferric oxide. Sulphuric oxide. 

The sulphates are easily reduced by bodies avid of oxygen, 
such as charcoal. 

If an intimate mixture of potassium sulphate with an excess 
of charcoal be heated to bright redness, and allowed to cool out 
of contact with the air, a black powder is obtained, which pro- 
duces a shower of sparks when projected into the air. It is 
the pyrophorous of Gray-Lussac. It owes its spontaneous in- 
flammability on contact with the air to finely-divided potassium 
sulphide which it contains, and which attracts oxygen with great 
avidity. The sulphide is formed according to the following 
reaction : 

K^SO^ + 4C = 4C0 + K'S 

Potassium sulphate. Potassium sulphide. 



CARBONATES. 275 

In the same manner barium sulphate and calcium sulphate 
are converted into sulphides by the action of charcoal at a high 
temperature. 

The other sulphates are also reduced under the same circum- 
stances, but the products vary; carbon dioxide or carbon mon- 
oxide and sulphurous oxide are disengaged, and the residue 
consists of either oxide or metal. 

Distinctive Characters. — AVhen treated by sulphuric acid, 
the sulphates do not evolve any gas. They do not deflagrate 
when thrown upon burning charcoal. Their solutions give a 
white precipitate of barium sulphate with barium nitrate, which 
is insoluble in nitric acid. When this precipitate is washed, 
dried, and calcined with an excess of charcoal, it leaves a resi- 
due of barium sulphide, and when this is moistened with hy- 
drochloric acid, it evolves hydrogen sulphide, which is easily 
recognized by its odor. 

CAEBONATES. 

Composition. — Carbonic acid is dibasic, like sulphuric acid. 
It is not known in the state of hydrate, and the carbonates are 
formed by the direct union of carbon dioxide with the metallic 
oxides or hydrates. 

When freshly-burnt lime is exposed to the air, it attracts at 
the same time the moisture and the carbonic acid gas of the air, 
and is converted into carbonate. 

CO'^ + CaO = CaCO^ 

Calcium oxide. Calcium carbonate. 

The carbonates then contain the group CO^ combined with 
a metal. In carbonic acid, this group would be united with two 
atoms of hydrogen. The composition of the more simple car- 
bonates is expressed by the following formulae: 

H^CO^ carbonic acid (unknown). 

■p r j 

TT \ CO^ acid carbonates (dicarbonates). 

R'^CO^ neutral carbonates. 
M"C03 neutral carbonates. 

In these formulae, R' represents a monatomic metal, such as 
potassium, which is equivalent to one atom of hydrogen. M" 
represents a diatomic metal, such as calcium, which is equiva- 
lent to two atoms of hydrogen. 

Properties. — Only the alkaline carbonates are soluble in pure 



276 ELEMENTS OF MODERN CHEMISTRY. 

water. The others are insokible, but they dissolve in water 
charged with carbonic acid. 

The soluble carbonates possess an alkaline reaction. It is 
the same with the acid carbonates of the alkaline metals, which 
are ordinarily called bicarbonates, such as potassium dicarbonate 
KHCOl 

All of the carbonates except the alkaline carbonates are de- 
composable by heat. In this decomposition carbon dioxide is 
disengaged, and there remains a residue of oxide, or of metal 
in case the oxide be reducible by heat. Thus, the carbonates 
of magnesium, calcium, zinc, lead, and copper leave a residue 
of oxide after calcination ; silver carbonate leaves a residue of 
metal. 

Barium carbonate is but slowly decomposed at a white heat ; 
its decomposition is facilitated by heating it in a current of 
steam. 

Bodies avid of oxygen act upon the carbonates as upon the 
oxides ; the metal is reduced if the base be reducible. Char- 
coal acts in this manner upon the carbonates. 

If cupric carbonate be heated with charcoal, carbon dioxide 
is disengaged, and metallic copper remains. 

2CuC0^ + C = 3C0^ + 2Cu 

Cupric carbonate. Copper. 

In this experiment carbon dioxide is disengaged, for cupric 
oxide is easily reducible by charcoal. It is not the same with 
potassium oxide ; hence potassium carbonate is only reduced 
by charcoal at a very high temperature with disengagement 
of carbon monoxide. 

K^CO^ -f 2C = SCO + K' 

When barium carbonate is heated with charcoal, carbon 
monoxide is disengaged in the same manner, but there remains 
a residue of barium oxide, for the latter is irreducible by char- 
coal. 

BaCO^ + C = 2C0 -f BaO 

Phosphorus decomposes all of the carbonates. 

A small piece of phosphorus may be placed at the bottom 
of a small test-tube, and the latter then nearly filled with well- 
dried sodium carbonate. The part of the tube containing the 
carbonate being heated to redness, the phosphorus may be 
heated so that its vapor will pass over the incandescent car- 



CLASSIFICATION OF THE METALS. 277 

bonate. The latter will be decomposed with the formation of 
sodium phosphate and a deposition of carbon. After cooling, 
the contents of the tube will be black. 

The experiment may be repeated upon calcium carbonate. 
The phosphorus is placed in a small crucible, which is then 
introduced into a larger one. The calcium carbonate (chalk) 
is then placed upon the lid of the smaller crucible, which is 
pierced with holes. The arrangement is heated upon a double 
grate, so that when the chalk has been brought to incandes- 
cence, the vapor of phosphorus may be caused to pass through 
it by placing some hot coals upon the lower grate. The chalk 
is rapidly decomposed, carbon monoxide is disengaged, and a 
mixture of calcium phosphate and phosphide is formed. This 
mixture serves for the preparation of hydrogen phosphide. 

Distinctive Characters. — When treated with sulphuric acid, 
the carbonates disengage a colorless, incombustible gas, which 
extinguishes burning bodies and produces a milkiness when 
agitated with lime-water. 



CLASSIFICATION OF THE METALS. 

In the preceding pages we have studied the composition and 
the general properties of metallic compounds. This study has 
revealed the fact that the metals possess very different aptitudes 
to form compounds, and various capacities of combination, which 
are manifested by the greater or less number of other atoms 
which the atoms of these metals can attract. In this respect, 
the differences existing between the metals are analogous to 
those which we have already remarked between the metalloids. 
On comparing the metals among themselves, some are discov- 
ered which resemble each other in the general structure of the 
compounds which they are capable of forming, and such can 
naturally be classed in the same group. On this plan the 
metals are divided into several families analogous to those first 
proposed by Dumas for the metalloids, and it will be seen that 
the general composition of the metallic compounds furnishes 
the elements for a natural classification of the metals. While 
this principle is excellent, its application is attended with some 
difficulties which chemistry has not j^et been able to solve. 
Consequently, this chapter must be limited to summary indi- 
cations upon the subject. 

Some of the metals are incapable of combining with more 
24 



278 



ELEMENTS OF MODERN CHEMISTRY. 



than a single atom of clilorino, bromine, or iodine. The com- 
pounds thus formed correspond in their atomic constitution to 
hydrochloric, hydriodic, and hydrobromic acids. On comparing 
potassium chloride or silver chloride to hydrochloric acid, it 
will be seen that an atom of potassium or an atom of silver 
occupies in them the place occupied by the hydrogen of the 
acid. The atoms of potassium and of silver are therefore 
equivalent to the atoms of hydrogen as far as their capacity 
of combination is concerned.. The other alkaline metals, such 
as sodium and lithium, are similar and belong to the same group. 
Their chlorides, bromides, and iodides, which are arranged in the 
following table, present analogous compositions : 



MoNATOMic Metals. 


MONATOMIC 

Chlorides. 


MONATOMIC 

Bromides. 


monatomic 
Iodides. 


Potassium K' 

Sodium Na' 

Lithium Li' 

Silver Ag' 


H'Cl 


RBr 


HI 


KCl 

NaCl 
LiCl 
AgCl 


KBr 

NaBr 

LiBr 

AgBr 


KI 

NaT 
Lil 

Agl 



These metals form oxides whose atomic constitutions corre- 
spond to that of water, each containing tAvo atoms of metal for 
one of oxygen. Their sulphides correspond to hydrogen sul- 
phide, containing two atoms of metal for one of sulphur. With 
the oxides and sulphides we may group the hydrates and 
sulphydrates, which possess analogous atomic constitutions. 

Type H20. Type H2S. 



OXIDKS. 


Hydrates. 


MONOSIILPHIDES. 


Sulphydrates. 


K-^O 


KOH 


K2S 


KSH 


Na20 


NaOH 


Na2S 


NaSH 


Ag'^0 




Ag2S 





The same analogy is continued between the salts of these 
metals, as will be seen from the nitrates and sulphates which 
we take as examples. , 

Nitric Acid, HNO^. Sulphuric Acid, H2S0-*. 



Nitrates. 


Sulphates. 


Acid Sulphates. 


KNO» 


K^SO* 


KHSO* 


NaN03 


Na2S04 


NaHSO* 


AgN03 


Ag2S04 





CLASSIFICATION OF THE METALS. 



279 



It is seen that in all of these compounds the metals under 
consideration replace hydrogen atom for atom ; each of them 
possesses the same capacity of combination as that gas. They 
are said to be monafomic. 

Certain other metals manifest a double capacity of combina- 
tion; one atom of any of these is capable of replacing two 
atoms of hydrogen, consequently it can combine with two 
atoms of chlorine, bromine, or iodine, or with one atom of 
oxygen or sulphur. In the chlorides of these metals, the two 
atomicities of the metal are satisfied by the two atomicities of 
two atoms of chlorine. In their oxides, the two atomicities 
of the metal are satisfied by the two atomicities or bonds of 
affinity which reside in one atom of oxygen. These metals are 
then diatomic. They are quite numerous and can be divided 
into several groups, one of the most natural of which com- 
prises barium, strontium, calcium, and lead. The following 
table shows the constitution of the principal compounds of 
these metals : 



Diatomic Metals. 


Chlorides. 


Oxides. 


Nitrates. 


Sulphates. 


Barium Ba" . 
Strontium Sr" . 
Calcium Ca" . 
Lead Pb" . . 


2HC1 


H20 


2HN03 


IPSO* 


BaC12 
SrC12 
CaCP 
PbCl2 


BaO 

SrO 
CaO 
PbO 


Ba(N03)2 
Sr(N03)2 
Ca(N03)2 

Pb(N03)2 


BaSO* 
SrSO* 
CaSO* 
PbSO* 



The metals of this group combine with oxygen in two pro- 
portions, forming not only the monoxides, IIO, but also the 
dioxides, RO^ They thus form two oxides, while they are 
capable of forming but one chloride, RCP. Thus, barium 
forms a monoxide, BaO, a dioxide, BaO^ and a dichloride, 
BaCP; but no tetrachloride of barium is known, and it is not 
probable that barium can act as a tetratomic element. How is 
it, then, that in the dioxide this metal can combine with two 
atoms of oxygen, while it cannot combine with four atoms of 
chlorine, which are equivalent to two atoms of oxygen ? In 
other words, what is the atomicity of barium in the dioxide 
which would seem to correspond to a tetrachloride ? It is 



280 ELEMENTS OF MODERN CHEMISTRY. 

undoubtedly diatomic in the dioxide as it is in tlie monoxide, 
and the constitution of barium dioxide is analogous to that of 
hydrogen dioxide, which has already been indicated. The 
two atoms of oxygen mutually satisfy two of their atomicities 
by combining together, and they retain two which are neutral- 
ized in combining with the diatomic atom of barium. Thus, 
in barium monoxide one atom of oxygen is joined to one atom 
of barium by both of its atomicities ; in the dioxide two atoms 
of oxygen are united to one atom of barium, each by one atom- 
icity. If we represent the saturation of two atomicities by a 
straight line, as has before been explained, we will have the 
following formulae : 



Ba:=0 


Ba 


Barium monoxide. 


/\ 




0-0 




Barium dioxide. 



In this manner, theory enables us to fix the relations existing 
between the atoms in a given body. 

The comparison may be continued between the other diatomic 
metals. Magnesium, the radical of magnesia, somewhat resem- 
bles calcium in its relations, and forms, as it were, the centre 
of a group including magnesium, zinc, cobalt, and nickel, and 
which is called the magnesium group. Manganese and iron, on 
one hand, and copper, on the other, seem to join this group by 
certain of their characteristics. In their most stable and gen- 
erally their most important compounds, these metals act as 
diatomic elements. All form the dichlorides RCP and the 
oxides HO. But in other compounds, manganese and iron 
seem removed from the metals of this group, and resemble 
chromium and aluminium. Copper, which resembles magne- 
sium in the series of cupric compounds, approaches mercury 
in the cuprous series. 

Bismuth, which might be classed with antimony, and gold 
are triatomic in their most important combinations. They 
form the chlorides BiCP and AuCP. 

A certain number of the metals may be grouped together as 
tetratomic^ since they manifest four atomicities in their principal 
combinations. They are tin, titanium, and zirconium. They 
form the chlorides RCP and the oxides RO^ In stannic chlo- 
ride, SnCl*, the tin is saturated with chlorine, of which it 
cannot combine with more than four atoms; it is tetratomic 
in this saturated compound. But it may combine with only 



CLASSIFICATION OF THE METALS. 



281 



two atoms of chlorine, thus forming the chloride SnCP, 
which is not saturated, for it can still fix two more atoms 
of chlorine. Tin only manifests two atomicities in the 
dichloride. 

In the same manner, ferrous chloride, FeCP, can absorb 
chlorine, becoming ferric chloride. The latter contains two 
atoms of iron and six of chlorine. These two atoms of iron 
exist in all the ferric compounds ; together they manifest six 
atomicities, for in ferric chloride they are united with six atoms 
of chlorine. They constitute a hexatomic couple. 



Compounds. 


Chlorides. 


Oxides. 


Sulphates. 


Ferric 

Manganic 

Chromic 

Aluminic 


Fe2Cl6 
Mn2Cl6 

Cr2Cl6 

A12C16 


Fe203 

Mn203 

Cr203 

A1203 


Fe2(S04)3 
Mn2(S04)3 
Cr2(S04)3 
A12(S04)3 



The following table gives a resume of the constitution of the 
principal metallic combinations. The metals there chosen as 
examples have different atomicities. The hexatomic couple, 
consisting of two atoms of iron, may for convenience be called 
ferricum. 



Metals. 


Chlorides, 


Oxides. 


Nitrates. 


Sulphates. 


Monatomic metal— Potassium K' . 


KCl 


K20 


KN03 


K2S04 


Diatomic metal— Barium Ba" . . . 


BaC12 


BaO 


Ba(N03)2 


BaSO* 


Triatomic metal— Bismuth Bi'" . . 


b;c]3 


Bi203 


Bi(N03)3 


Bi2(S04)3 


Tetratomic metal— Tin Sniv . . , 


SnC14 


Sn02 






Hexatomic group— Ferricum (re2)vi 


re2C16 


re203 ,Fe2(N03,6 


re2(S0i)3 



Such are the principles furnished by the theory of atomicity 
for a rational classification of the metals. 



24* 



282 ELEMENTS OP MODERN CHEMISTRY. 

POTASSIUM. 

K = 39.1. 

Potassium was discovered by Sir Humphry Davy in 1807. 
It ordinarily occurs in commerce in gray, globular masses, 
readily yielding to the pressure of the nail. It has a dull, 
tarnished appearance, but when freshly cut it exposes a brilliant 
surftice. It is the metallic radical of potash. 

If a fragment of this metal be thrown into water, it at once 
takes fire and rushes about on the surface of the liquid, burn- 
ing with a violet flame. Finally, it disappears with a little 
explosion. 

This brilliant phenomenon is due to the energy with which 
potassium decomposes water. 

2H^0 + K^ = 2K0H + H^ 

The hydrogen which is disengaged is inflamed by the incan- 
descent metal. The potassium hydrate formed ultimately dis- 
solves in the water, but its temperature being very high at the 
moment of its solution, and its combination with the water 
also producing heat, there results a sudden formation of steam, 
which gives rise to the little explosion. 

Preparation and Properties. — Potassium is prepared by 
decomposing potassium carbonate by carbon at a high tempera- 
ture. 

K^CO^ + 20 = 3C0 + K^ 

Potassium carbonate. Carbon monoxide. 

The mixture is heated to whiteness in an iron retort and the 
vapors are passed into a copper receiver. The potassium dis- 
tils and condenses in globules or irregular masses, still contain- 
ing charcoal and a black substance. It is purified by redistilla- 
tion in an iron retort, and is condensed in a copper receiver 
filled with naphtha. The manufacture of potassium is a dan- 
gerous operation. It is accompanied by the formation of 
various accessory products, among which is a black substance 
which sometimes explodes spontaneously on contact with the 
air. 

Potassium melts at 62.5° (Bunsen). It boils at a red heat, 
and its vapor is green. When exposed to the air, it rapidly 
absorbs oxygen and at the same time decomposes the atmos- 
pheric moisture. It inflames at a temperature but slightly 
elevated and becomes converted into oxide. 



POTASSIUM OXIDES. — POTASSIUM HYDRATE. 



28^ 



POTASSIUM OXIDES. 

Potassium monoxide^ K'^O, is formed when thin pieces of 
the metal are abandoned to the action of dry air, or when 
potassium hydrate is heated with potassium. 

2K0H + K^ =: 2K^0 + W 
It is a grayish-white substance which unites with water with 
extreme violence, forming potassium hydrate. 
K^O + H-'O = 2K0H 
A tetroxide of potassium, K'^0*, is formed when potassium 
is heated in an excess of oxygen, but it is little known. 

POTASSIUM HYDRATE, OR CAUSTIC POTASSA. 
KOH 
This important compound is prepared by boiling 1 part of 
potassium carbonate with 12 parts of water, and gradually add- 
ing milk of lime to the boiling liquid. The lime combines 
with the carbonic acid forming an insoluble carbonate, while 
the potassa remains in solution. 

K^CO^ + Ca(0H)2 = CaCO^ + 2K0H 

Calcium hydrate. Calcium carbonate. 

When the decomposition is finished the liquid is allowed to 
settle, and the clear solution decanted and rapidly evaporated. 




Fig. 97. 



The residue is melted in a silver dish and poured out upon flat 
stone slabs or cast in cylindrical metallic moulds (Fig. 97). 

This product is known as potash hy lime. It is impure. 
By treating it with alcohol, which dissolves only the potassium 



284 ELEMENTS OF MODERN CHEMISTRY. 

hydrate, it may be purified from lime, and the salts of potas- 
sium it may contain, and especially the carbonate, which is 
formed by the absorption of carbonic acid gas from the air 
during the evaporation. The clear alcoholic solution is decanted, 
and after the alcohol has been expelled by distillation, the resi- 
due is evaporated to dryness and fused in a silver dish. It is 
known as potash by alcohol. 

Recently-fused potassium hydrate occurs as opaque, white 
fragments having a short fibrous fracture and a density of 2.1. 
It melts at a red heat and volatilizes at whiteness ; it is not 
decomposed by heat. When exposed to the air, it absorbs moist- 
ure and carbonic acid gas, and deliquesces. It is very soluble 
in water, and produces heat in dissolving. A hydrate, KOH 
-]- 2H^0, is deposited from its hot and very concentrated solu- 
tion in acute rhombohedra. 

Potassium hydrate is decomposed by iron at a white heat : 
oxide of iron is formed, and hydrogen and potassium vapor are 
disengaged. Gay-Lussac and Thenard founded a process for 
the preparation of potassium on this decomposition. Until then 
the metal had only been obtained in small quantities by Davy 
by the electrolysis of potassium hydrate. 

Potassium hydrate is very caustic. It softens and destroys 
the skin, and for this purpose is employed in surgery as a caustic. 
It manifests the properties of an alkali in the highest degree ; 
these are its solubility in water, its power to neutralize the 
acids and decompose a great number of metallic solutions, and 
its corrosive action on the tissues. This alkalinity may be shown 
by the energy with which the most feeble solutions of potassa 
restore the blue color to reddened litmus, and change to green 
the tincture of violets. 

SULPHIDES OF POTASSIUM. 

Potassium will burn in vapor of sulphur. It unites with 
the latter body in five different proportions, forming the sul- 
phides K^S, K'^S^ K2S^ K'S*, and K^S^ 

Potassium monosiilphide is formed when potassium sulphate 
is heated to redness in a current of hydrogen, or in a brasqued^ 
and covered crucible with charcoal. 

1 A bi-asqued crucible is a clay crucible into which powdered charcoal 
moistened with gum-water has been strongly pressed, and afterwards cal- 
cined. The substance to be reduced is placed in a cavity hollowed out in 
the charcoal. 



POTASSIUM CHLORIDE. — POTASSIUM IODIDE. 285 

K^SO* -\- 4C = 4C0 -f K^S 

Potassium sulphate. Potassium monosulpbide. 

A reddish, deliquescent, and caustic mass is thus obtained. 
When a mixture of sulphur and potassium carbonate is fused, 
carbon dioxide is disengaged, and a brown mass is obtained on 
cooling, which is known as liver of sulphur. It is a mixture 
of potassiimi polysulphide with undecomposed carbonate and 
potassium sulphate or hyposulphite, according to the tempera- 
ture and the proportions of sulphur which have been employed. 
With an excess of sulphur, potassium pentasulphide is obtained. 
Liver of sulphur dissolves in water with a brown-yellow color. 

Potassium pentasulphide and hyposulphite are also formed 
when potassium hydrate is boiled with an excess of flowers of 
sulphur. The filtered solution is brown. When treated with 
hydrochloric acid, it evolves hydrogen sulphide, and finely- 
divided, yellowish, pulverulent sulphur is deposited. 

K'S^ + 2HC1 = 2KC1 + ff S + S* 

POTASSIUM CHLORIDE. 

KCl 

This salt is found crystallized in cubes in the neighborhood 
of certain fissures of A^esuvius, and in thin layers in the saline 
deposits at Stassfurth, Prussia, and in other localities. At 
Stassfurth there is found a double chloride of potassium and 
magnesium, KCl,MgCP -{- 6H'0. When this double salt is 
dissolved in hot water, the greater part of the potassium 
chloride is deposited on cooling while the magnesium chloride 
remains in solution. 

Potassium chloride crystallizes in cubes, but it sometimes 
separates in octahedra from solutions containing free potassa. 
It is unaltered by the air. Its taste is analogous to that of 
sodium chloride ; it is more soluble in water than the latter, 
and produces a greater depression of temperature in dissolving. 
1 part of chloride of potassium dissolves in 3 parts of water 
at 17.5°. 100 parts of water at 0° dissolve 29.23 parts of 
potassium chloride and 0.2738 additional for each degTee of 
temperature. 

POTASSIUM IODIDE. 
KI 

This compound is quite important on account of its use in 
medicine. It is obtained by adding powdered iodine to solution 



286 ELEMENTS OF MODERN CHEMISTRY. 

of potassium hydrate until the latter is completely neutralized. 
Potassium iodide and iodate are formed, the latter being pre- 
cipitated. The whole is evaporated to dryness, and the residue 
heated to redness, by which the iodate is converted into iodide. 
The mass is redissolved in boiling water and the solution con- 
centrated ; fine cubical crystals of potassium iodide are obtained 
on cooling. 

These crystals are opaque and anhydrous. They melt at a 
red heat without decomposition ; their taste is salty and some- 
what bitter. 100 parts of water at 18° dissolve 143 parts of 
potassium iodide. 

A solution of potassium iodide dissolves iodine abundantly, 
assumino- a dark-brown color. 

o 

If nitric acid be added to a solution of potassium iodide, 
iodine is at once deposited and red vapors are disengaged if 
the solution be concentrated (page 131). 

This decomposition of potassium iodide takes place even in 
very dilute solutions. It may serve for the detection of the 
smallest trace of this salt if a solution of starch be previously 
added to the liquid ; in this case a blue color will be produced. 

Potassium bromide is prepared by a process similar to that 
which yields potassium iodide. It crystallizes in cubes which 
are soluble in about 1.5 parts of cold water. 

POTASSIUM NITRATE. 
KN03 

This important salt, long known as nitre and saltpetre, im- 
pregnates the soil and sometimes effloresces upon its surface in 
certain regions of India, Egypt, Persia, Hungary, and Spain. 
In the United States, it is found in many localities, generally 
in caverns in limestone rock, called saltpetre caves. It is 
obtained by lixiviating the earthy matters containing it and 
evaporating the solution. 

It is less abundant in northern climates. It is formed 
wherever nitrogenized organic substances decompose in pres- 
ence of potassa. Thus, it exists in small quantities in the soil 
of cellars, in moist walls, and in the debris of demolitions. 
In these cases it is mixed with a certain quantity of sodium 
nitrate and a large excess of calcium and magnesium nitrates. 
Formerly such materials were* lixiviated to obtain the nitrates, 
all of which were then converted into potassium nitrate. Nitre 
is also manufactured artificially by exposing to the air mixtures 



POTASSIUM NITRATE. 287 

of animal matters with wood-ashes and lime which are fre- 
quently moistened with stale urine or stable-drainings. How- 
ever, a great part of the potassium nitrate employed in the 
arts is now obtained from the natural sodium nitrate of Peru. 
Two processes are employed. 

One consists in adding the sodium nitrate to a concentrated 
boiling solution of potassium carbonate : sodium carbonate 
being less soluble than the latter, is precipitated and continues 
to deposit during the concentration ; it is removed, and the 
potassium nitrate, which is very soluble in hot water, crystal- 
lizes out on cooling. 

The second process consists in decomposing the sodium nitrate 
with potassium chloride. The saturated and boiling mixture 
of the two solutions deposits sodium chloride, which is sepa- 
rated, and the potassium nitrate crystallizes on cooling. 

Properties. — This salt crystallizes from its aqueous solution 
in long, six-sided prisms, terminated by six-sided pyramids. Gen- 
erally these crystals are grooved or striated. They belong to the 
right rhombic system. Their taste is cooling and slightly bitter. 

Potassium nitrate melts at about 350° ; at a higher tem- 
perature it disengages oxygen and is converted into potassium 
nitrite, KNO^, which is in its turn decomposed at a red heat, 
leaving a mixture of oxide and peroxide of potassium. 

Potassium nitrate is very soluble in hot water: 100 parts of 
water at 0° dissolve only 13.32 parts of the salt, but at 18° they 
dissolve 29 parts ; at 97°, 236 parts ; and at 100°, 246 parts. 

The facility with which potassium nitrate parts with its oxy- 
gen, of which it contains nearly half its weight, renders it an 
energetic oxidizer of many bodies. 

If a small quantity of pulverized saltpetre be thrown upon 
glowing coals, the salt melts and decomposes, increasing the 
combustion at the point of contact with the fuel : it is said to 
deflagrate upon hot coals. The nitrate becomes converted into 
carbonate. 

Gunpowder is an intimate mixture of saltpetre, charcoal, 
and sulphur. As is well known, the combustion of this sub- 
stance is instantaneous, and gives rise to the sudden formation 
of gaseous products. The decomposition may be expressed 
generally by stating that the charcoal combines with the oxy- 
gen of the nitre to form carbon dioxide and carbon monoxide ; 
the nitrogen is liberated, and the sulphur combines with the 
potassium forming potassium sulphide. As the mixture con- 



288 ELEMENTS OF MODERN CHEMISTRY. 

tains all of the oxygen necessary for its own combustion, the 
latter can be effected in a limited and closed space. It can 
readily be understood that the explosive energy of the powder 
is due to a sudden evolution of gas occupying many times the 
volume of the powder, and of which the volume is still further 
augmented by the high temperature. 

POTASSIUM SULPHATE. 
K2S0* 

This salt is obtained as a by-product in various industrial 
operations. It deposits from the mother-liquors of the soda 
from sea-weed when these are exposed to low temperatures. It 
may be made by saturating with potassium carbonate the potas- 
sium acid sulphate which is formed in the preparation of nitric 
acid by the decomposition of potassium nitrate with sulphuric 
acid, a process which is now but little employed. 

It crystallizes in four-sided prisms or in double, six-sided 
pyramids belonging to the orthorhombic system. These crys- 
tals are hard, anhydrous, unaltered by the air, and melt at a 
red heat without decomposition. They are but slightly soluble 
in water and insoluble in absolute alcohol. 100 parts of water 
at 0° dissolve 8.36 parts, and 0.1741 part for each additional 
degree of heat. 



POTASSIUM ACID SULPHATE. 

This salt may be obtained by fusing 13 parts of the neutral 
sulphate with 8 parts of concentrated sulphuric acid. The 
saline mass is dissolved in boiling water, and the solution when 
properly concentrated deposits rhombic octahedra or tabular 
crystals belonging to the orthorhombic system. 

Potassium acid sulphate is much more soluble in water than 
the neutral salt ; its solution is acid. When strongly heated, 
it first gives up water and then sulphuric oxide, leaving a resi- 
due of neutral sulphate. 

POTASSIUM CHLORATE. 

KC103 
This salt is formed, together with potassium chloride, by the 
action of chlorine upon a concentrated solution of potassium 
hydrate or carbonate : 

6C1 -f 6K0H = KC10=^ + 5KC1 + SH^O 



POTASSIUM PERCHLORATE. 289 

It is less soluble than the chloride, and is consequently de- 
posited in great part as the solution becomes saturated with 
chlorine. It is purified by several recrystallizations. 

In the arts, it is obtained by the action of chlorine upon a 
mixture of lime, potassium chloride, and water, heated in closed 
vessels. Chlorate and chloride of calcium are formed, and in 
presence of the potassium chloride, a double decomposition takes 
place, potassium chlorate and calcium chloride, which is very 
soluble, being formed. The liquid is filtered hot, and the potas- 
sium chlorate crystallizes out on cooling. 

KCl + 3CaO + 3CP = KCIO^ + 3CaCP 

Calcinin oxide. Calcium chloride. 

Potassium chlorate crystallizes in colorless, rhomboidal tables. 
When very thin they present an iridescent reflection. It melts 
at 400°, and at a higher temperature is decomposed into oxygen 
and chloride and perchlorate of potassium, the latter of which 
is also decomposed when the temperature is raised still further. 

2KC10'^ = KCl + KCIO* 4- 0^ 
KCIO* = KCl -4- 0* 

Potassium chlorate deflagrates when thrown upon hot coals ; 
when mixed with sulphur, it explodes by friction or percussion ; 
the detonation becomes dangerous if the sulphur be replaced 
by phosphorus. 

It is not very soluble in cold water. 100 parts of water at 
0° dissolve 3.3 parts, and at 24°, 8.44 parts. It is much more 
soluble in boiling water. 

POTASSIUM PERCHLORATE. 

KCIO* 

This salt is formed by the action of either heat or sulphuric 
acid upon potassium chlorate (page 124). It is but slightly 
soluble in water, requiring 65 parts at 15° for its solution. It 
crystallizes in anhydrous and transparent right rhombic prisms.- 
Above 400° it decomposes into potassium chloride and oxygen. 

POTASSIUM CARBONATES. 

Potassium Neutral Carbonate, K^COl — This carbonate 
is found in commerce under the simple name potash, and is 
known according to its source as Russian or American potash; 
N 25 



290 ELEMENTS OF MODERN CHEMISTRY. 

It is obtained by lixiviating wood ashes ; that is, exhausting 
them with water, evaporating the solution to dryness, and cal- 
cining the residue in the air. The potash thus obtained is 
impure carbonate mixed with other salts of potassium, princi- 
pally the chloride and sulphate, and small quantities of silicate. 
It contains from 60 to 80 per cent, of carbonate. 

Potassium carbonate is now manufactured from the native 
chloride, Stassfurth salt, by a process similar to that which will 
be described for the manufacture of sodium carbonate from 
common salt. 

Pure potassium carbonate may be prepared by calcining potas- 
sium acid tartrate, or cream of tartar, at a red heat. A black 
mass is thus obtained from which water dissolves pure potas- 
sium carbonate, and the solution is evaporated to dryness. 

Neutral potassium carbonate is very soluble in water, and 
absorbs moisture from the air. 1 part of the anhydrous salt 
dissolves in 1.05 parts of water at 3°, and in 0.49 parts at 70° 
(Osann). The solution has a decided alkaline reaction. A 
very concentrated hot solution deposits rhombic octahedra 
containing K^CO^ -|- 2W0 on cooling. 

Potassium Acid Carbonate, KHCOl — When a current of 
carbonic acid gas is passed into a concentrated solution of potas- 
sium neutral carbonate, the gas is absorbed, and crystals of 
potassium acid carbonate, ordinarily known as bicarbonate of 
potassa, are formed. 

It represents carbonic acid in which a single atom of hydro- 
gen is replaced by an atom of potassium. 

C02 + IPO = H^CO^ carbonic acid (hypothetical). 
C02 + KHO =r „ i CO'' potassium acid carbonate. 
CO'-^ + K20 = K2C03 potassium carbonate. 

Potassium acid carbonate readily crystallizes in oblique rhom- 
bic prisms. It is much less soluble in water than the neutral 
carbonate, and its solution disengages carbonic acid gas on 
boiling. Its reaction is alkaline. 

Characters of Potassium Salts. — The salts of potassium 
communicate a violet tint to flame. Their solutions are not 
precipitated either by hydrogen sulphide, ammonium sulphide, 
or sodium carbonate. 

Perchloric acid occasions a white precipitate of potassium 
perchlorate. 



SODIUM. 



291 



Platinum tetrachloride produces a yellow, crystalline precipi- 
tate of platinum and potassium double chloride, 2KCLPtCl^ 

Hydrofluosilieic acid forms a white, gelatinous precipitate 
consisting of potassium fluosilicate. 



SODIUM. 

Xa = 23 

Sodium was discovered by Sir Humphry Davy in 1807. It 
is made by decomposing sodium carbonate with charcoal, a 
certain proportion of chalk being added to render the mixture 
infusible. The operation is conducted in large cast-iron cylin- 




ders covered with a refractory luting to enable them to resist 
the high temperature required to effect the decomposition. 
The vapor passes into a flattened receiver in which the sodium 
condenses, and from which it runs into appropriate vessels 
(Fig. 98). 



292 ELEMENTS OF MODERN CHEMISTRY. 

This metal is soft at the ordinary temperature. It has a 
silvery lustre, melts at 90.6°, and distils at a red heat. It is 
not as avid of oxygen as potassium ; it can be melted in the 
air without taking fire. When thrown upon water, it melts 
and runs around on the surface, producing a hissing noise. 
The water is decomposed with disengagement of hydrogen and 
the formation of sodium hydrate. The reaction is analogous 
to that of potassium upon water, but is less energetic; fre- 
quently, however, it terminates by an explosion. 

If sodium be thrown upon hot water, or water which has 
been thickened with gum or starch, so that the consistence 
of the liquid may prevent the globule from moving rapidly, 
the latter becomes sufficiently heated to ignite the hydrogen 
evolved, which then burns with a yellow flame. 



The compounds of sodium are widely difiused in nature, and 
generally present great analogies with the corresponding potas- 
sium compounds. 

OXIDES AND HYDRATE OF SODIUM. 

Two oxides of sodium are known, a monoxide, Na^O, and a 
dioxide, Na^Ol 

Sodium hydrate^ NaOH, is frequently employed in the lab- 
oratory and in the arts under the name caustic soda. It is 
prepared by decomposing a rather dilute, boiling solution of so- 
dium carbonate by milk of lime, in the manner described for 
the preparation of potassium hydrate (page 283). It occurs 
as a white solid, which attracts moisture and carbonic acid 
from the air, and finally becomes transformed into a dry mass 
of carbonate. Sodium hydrate is freely soluble in water, and is 
very caustic. It is known in commerce as concentrated lye. 

SODIUM SULPHIDE AND SULPHYDRATE. 

Sodium sulphide, Na'"^S, is prepared by the following pro- 
cess: A concentrated solution of sodium hydrate is divided 
into two equal parts ; one part is then saturated with hydrogen 
sulphide, sodium sulphydrate being formed. 

NaOH + H^S = NaSH -f H^O 

Sodium hydrate. Sodium sulphydrate. 



SODIUM CHLORIDE. 293 

To this sulpliydrate the other portion of sodium hydrate is 
added, and the solution is concentrated out of contact with the 
air. Hydrated crystals of sodium sulphide are deposited. 

NaSH + NaOH = WO -f Na^S 

These crystals are rectangular prisms terminated by four- 
faced points. When pure, they are colorless; they are very 
soluble in water. 

SODIUM CHLORIDE. 

NaCl 

This body is common salt, or sea-salt. It is widely diffused 
in nature. It is found in the solid state, as rock-salt, in large 
deposits in many countries. 

Sea-water contains a large proportion of sodium chloride, 
and this salt also exists in a number of mineral waters, of 
which it forms the most abundant constituent. 

In France, the greater portion of the salt delivered to com- 
merce is obtained by the evaporation of sea-water in the salt- 
marshes near the ocean, and the salt-basins along the Mediter- 
ranean. These are extensive basins into which the water is 
led from the sea, and where it forms a shallow layer, which is 
continually swept by the summer winds. It thus becomes con- 
centrated, and the concentration is favored by the water being 
continually kept in motion from one basin to another, until it 
arrives in the areas where the salt is deposited. The mother- 
liquors, from which the sodium chloride is separated, and which 
are still saturated with that salt, contain, in addition, magne- 
sium sulphate and salts of potassium. By cooling them to a 
low temperature sodium sulphate is obtained, being formed by 
a double decomposition between the sodium chloride and the 
magnesium sulphate. The new mother-liquor then deposits, 
first, potassium and magnesium double sulphate, and after- 
wards, magnesium and potassium double chloride (Balard). It 
was in the latter of these liquors that Balard discovered bro- 
mine in 1826. 

Sodium chloride is also obtained by the evaporation of the 
waters of salt springs. The operation is conducted in large 
sheet-iron boilers ; the salt crystallizes from the hot liquid, and 
a double sulphate of calcium and sodium, which is but slightly 
soluble, deposits in the basins in the course of time. 

25* 




294 ELEMENTS OF MODERN CHEMISTRY. 

Sodium chloride crystallizes from its aqueous solution in 
cubes. The crystals are generally small, and a great number 
of them frequently become agglomer- 
ated in symmetrical hopper-like masses 
(Fig. 99). These crystals are anhy- 
drous, but contain a small quantity of 
interposed water ; when heated they 
decrepitate, because this water is vola- 
FiG. 99. tilized and suddenly separates the crys- 

tals. Rock-salt is sometimes found in 
transparent cubes, sometimes in octahedra and intermediate 
forms. Sodium chloride fuses at a red heat and solidifies to a 
crystalline mass on cooling. It volatilizes at a white heat. It 
is very soluble in water, and its solubility does not increase with 
the temperature. According to Gay-Lussac, 

1 part of common salt dissolves in 2.78 parts of water at 14° 
" " '<■ 2.7 " " 60° 

" " « 2.48 " " 109.7° 

The saturated solution boils at 109.Y° ; its density at 8° is 
1.205. Sodium chloride is insoluble in absolute alcohol. 



SODIUM SULPHATE. 

This salt is obtained in the arts by decomposing common salt 
with sulphuric acid (page 117). 

This operation, which constitutes the first step in the manu- 
facture of sodium carbonate, is conducted in a reverberatory 
furnace, connected with a suitable apparatus for the condensa- 
tion of the hydrochloric acid which is disengaged. Sodium 
acid sulphate is first formed, and at a higher temperature this 
reacts upon another molecule of sodium chloride. 

^JSO* + NaCl = Na^SO* + HCl 

Sodium acid suliihate. Sodium sulphate. 

Sodium sulphate is now extensively produced by subjecting 
the mother-liquors from the manufacture of salt from sea-water 
to intense cold. 

It crystallizes from water in four-sided, oblique rhombic 
prisms, containing 10 molecules of water of crystallization; 



SODIUM CARBONATE. 295 

these crystals effloresce in the air. They possess a bitter, salty, 
and disagreeable taste. They are very soluble in water, and 
the temperature of their maximum solubility is 33°. Accord- 
ing to Gay-Lussac, 

100 parts of water at 0° dissolve 12 parts of sodium sulphate. 

u ^ (( 18° " 48 " " 

u « 25° " 100 « " 

« •< 33° *' 332.6 " " 

^ " 50° " 263 " « 

When the solution saturated at 33° is heated, it deposits an- 
hydrous sodium sulphate in orthorhombic octahedra, analogous 
to the anhydrous sodium sulphate found in nature {theRardite). 

Sodium Acid Sulphate, g.l SO^— This salt may be ob- 
tained by dissolving in water the requisite proportions of so- 
dium neutral sulphate and sulphuric acid. On cooling the 
saturated solution, oblique rhombic prisms are obtained, which, 
according to Mitscherlich, contain two molecules of water of 
crystallization. These crystals are Tery soluble in water, and 
have an acid taste. Alcohol decomposes them into sulphuric 
acid, which dissolves, and neutral sulphate, which precipitates. 



SODIUM CARBONATE. 

Na2C03 

This important salt, known also as soda and sal-soda^ is 
manufactured on an immense scale in the arts. It is used in 
the manufacture of soap and glass, for washing, and many other 
purposes. It was formerly obtained from the ashes of fuci, 
algae, and other sea-plants which furnished Alicant soda. It 
is now most generally prepared from sodium chloride, and the 
process, which is due to Le Blanc, consists of three distinct 
operations: 1st, the transformation of the sodium chloride 
into sulphate by sulphuric acid ; 2d, the conversion of the sul- 
phate into carbonate by calcination with a mixture of chalk 
and coal; 3d, lixiviation of the calcined mass and evaporation 
of the solution. Only the latter two operations need be de- 
scribed here : they are conducted in reverberatory furnaces, 
of which the doubly-arched roofs are licked by the flame of 
the combustible (Fig. 100). 



296 



ELEMENTS OF MODERN CHEMISTRY. 



A mixture of 1000 parts of sodium sulphate, 1040 parts of 
chalk, and 580 parts of coal, is first introduced into compart- 
ment B of the furnace, where it is dried. It is then transferred 
to compartment A, where the temperature is very elevated, 
and where the sodium sulphate is reduced to sulphide by the 




Fig. 100. 

coal. The sodium sulphide and chalk react upon each other, 
forming sodium carbonate and calcium sulphide (Kolb). 

The results of the reaction may be expressed by the follow- 
ing equation : 

Na^SO* + CaCO^ + C* =-- Na'^CO^ + CaS. + 4C0. 

There are, however, certain secondary reactions which take 
place at the same time ; thus, a certain quantity of sodium 
oxide is formed by the action of the coal upon the carbonate. 

Na^CO^ + C = 2C0 + Na^O 

When the incandescent mass has become pasty, it is removed 
from the furnace, reduced to powder, and thoroughly lixiviated. 
The water dissolves the sodium carbonate, and leaves the in- 
soluble calcium sulphide, which remains mixed with the lime 
produced by the decomposition of the excess of chalk employed 
(Grossage, Scheurer-Kestner). The solutions are concentrated 
in the boiler D, heated by the waste heat from the soda fur- 
nace. Finally, they are drawn off into the compartment C, 
where they are evaporated to dryness. The sal-soda of com- 
merce is thus obtained. When the properly-concentrated solu- 
tion is allowed to cool, the crystallized soda of commerce is 
deposited. 

Another process, proposed by Schlcesing and Rolland, is also 
used for the fabrication of sodium carbonate. 



SODIUM CARBONATE. 29*7 

It depends upon the double decomposition which takes place 
between ammonium acid carbonate and sodium chloride in 
concentrated aqueous solution. 

NaCl + (NH*}HCO^ = NH^Cl + NaHCO' 

The sodium acid carbonate, which is but slightly soluble, is 
precipitated ; it is collected and converted into the neutral car- 
bonate by the action of heat. 

2NaHC0' = Na'^CO' + CO^ + H^O 

It thus loses half of its carbonic acid, which is utilized for 
the preparation of a new quantity of ammonium acid carbonate. 
The other portion of the carbonic acid necessary for this oper- 
ation is produced by the calcination of lime-stone (calcium car- 
bonate), which at the same time yields the lime necessary for 
the liberation of the ammonia contained in the mother-liquor 
in the form of ammonium chloride. 

A considerable quantity of sodium chloride is also manufac- 
tured from cryolite, which is a double fluoride of sodium and 
aluminium, and of which large deposits exist in Greenland. 
The mineral is calcined with lime, calcium fluoride and alumi- 
nate of soda being formed. 

APFP,6NaFl + 6CaO = 6CaFP + AP0^3Na^0 

Cryolite. Calcium fluoride. Aluminate of soda. 

The latter compound is dissolved out by water and decom- 
posed by carbonic acid gas, aluminium oxide being precipitated 
and sodium carbonate remaining in solution. 

Sodium carbonate crystallizes in oblique rhombic prisms, 
containing 10 molecules of water of crystallization. When 
heated, they fuse in this water of crystallization, which they 
then abandon ; they also lose it by efflorescence when exposed 
to the air. 

Sodium carbonate is very soluble in water, and the solution 
has a strongly alkaline reaction. According to Poggiale, 

100 parts of water at 0° dissolve 7.08 parts of sodium carbonate. 
" " 10° " 16.06 " " 

« u 20° " 25.93 « " 

« " 25° " 30.83 " " 

« " 30° " 35.90 " " 

" a 104.6° " 48.5 " " 

The saturated solution boils at 104.6°. » Sodium carbonate 
is insoluble in alcohol. 



298 ELEMENTS OP MODERN CHEMISTRY. 

Sodium Acid Carbonate, NaHCO^ — When carbonic acid 
gas is passed into a solution of sodium carbonate or over 
crystals of that salt, the gas is absorbed and sodium acid car- 
bonate, commonly called bicarbonate of soda, is formed. This 
salt crystallizes in oblique, four-sided prisms, shortened into the 
form of tables. Its taste is salty and slightly alkaline. It is 
less soluble in water than the neutral carbonate. It restores 
the blue color to reddened litmus ; its solution does not pre- 
cipitate that of magnesium sulphate. When boiled, it loses 
carbonic acid, neutral carbonate being formed. 



PHOSPHATES OF SODIUM. 

There are three phosphates of sodium derived from ordinary 
or otho-phosphoric acid. 



H V PC* 

hJ 


H ^ PO* + 2H20 Na [ PC* + 12H20 
HJ hJ 


Na-j 

Na V PC* + 12^-20 

NaJ 


Phosphoric 
acid. 


Monosodium Disodium phosphate, 
phosphate. 


Trisodium phosphate. 



Monosodium phosphate is acid, the disodium is neutral, and 
the trisodium has an alkaline reaction. Disodium phosphate, or, 
as it is frequently called, common or neutral phosphate of soda, 
is the most important. It is prepared by neutralizing the cal- 
cium acid phosphate, obtained by digesting bone-dust with dilute 
sulphuric acid and filtering, with sodium carbonate. Tricalcium 
phosphate is precipitated, and disodium phosphate remains in 
solution. By evaporation of the filtered liquid, the salt may 
be obtained in voluminous, transparent, oblique rhombic prisms, 
containing 12 molecules of water of crystallization. 

SODIUM BORATE, OB BORAX. 

This salt corresponds to a boric acid containing 2Bo^O^ -|- 
H'O = H'^Bo^O^ It results from the action of one molecule 
of sodium oxide upon two molecules of boric oxide. 

2(Bo^O=') -f Na^O = Na^Bo^O' 

It crystallizes with either 10 or 5 molecules of water. 
Borax was formerly obtained from Asia, where it exists in 
solution in the waters of certain lakes. By the evaporation 



LITHIUM. 299 

of these waters a product known as tinhal was obtained ; this 
is natural borax; it crystallizes in oblique rhombic prisms. 
Borax is found in abundance in certain lakes in California. 
A great part of the borax of commerce is obtained by satu- 
rating the boric acid of Tuscany with sodium carbonate, and 
causing the solution to crystallize below 56°. If the boiling 
solution be very concentrated, it deposits between 79 and 56° 
crystals which are octahedral and contain only 5 molecules 
of water of crystallization. The two varieties of borax, the 
prismatic and the octahedral, differ then in their proportions 
of water of crystallization. 

When borax is heated, it melts in its own water, swells up 
and becomes dry, and then undergoes igneous fusion. Melted 
borax dissolves a great number of oxides and forms with them 
variously-colored glasses on cooling. It dissolves in 12 parts 
of cold and 2 parts of boiling water ; the solution has a faint 
alkaline reaction. 

Characters of Sodium Salts. — Sodium salts are not pre- 
cipitated from their solutions by either hydrogen sulphide, 
ammonium sulphide, sodium carbonate, or platinic chloride. 
Hydrofluosilicic acid forms with them a white precipitate. A 
solution of potassium antimonate produces a white precipitate 
of sodium antimonate (Fremy). 

Sodium salts impart a yellow color to flames. 

A small quantity of alcohol may be ignited in a saucer and 
will burn with an almost colorless flame, but the introduction 
of a small quantity of sodium hydrate, chloride, or any other 
sodium compound, at once colors the flame bright yellow. 

This character is very sensitive, and the smallest trace of 
sodium may thus be recognized by introducing a platinum wire, 
dipped into the substance to be tested, into the colorless flame 
of the blow-pipe or of a Bunsen burner. 



LITHIUM. 

Li = 7 

In 1817, Arfvedson, a Swedish chemist, discovered a new 
alkali, lithia, which is the hydrate of lithium, LiOH, analogous 
to potassium hydrate, KOH. To this hydrate corresponds an 
oxide, Li'O, and a chloride, LiCl. Bunsen was the first to ob- 
tain the metal lithium, which he prepared by electrolysis of the 



300 ELEMENTS OF MODERN CHEMISTRY. 

fused chloride. It is a silvery-white metal, but its surface rap- 
idly tarnishes in the air. It is the lightest of the solid ele- 
ments, its density being between 0.5*78 and 0.589. It melts at 
180°. It is less oxidizable than either sodium or potassium. 
When heated above its point of fusion in the air or in oxygen, 
it burns with a brilliant white flame. It decomposes water at 
ordinary temperatures, but without melting like sodium. 

The salts of lithium are soluble in water, but the carbonate 
and phosphate only slightly so. There exists also a double 
phosphate of sodium and lithium, which is but slightly soluble. 
The salts of lithium communicate a red color to the flame of 
alcohol or of the Bunsen burner. 

The compounds of lithium are generally prepared from the 
native silicate known as lepidolite. 



CESIUM AND KUBIDIUM. 

SPECTRUM ANALYSIS. 

Caesium and rubidium are two alkaline metals discovered 
by Kirchhoff" and Bunsen in 1860-61, by the aid of a new 
method of analysis. This method consists in the examination 
of spectra ; hence the name spectrum analysis. 

The solar spectrum formed upon a screen which intercepts a 
beam of solar light refracted by passage through a prism, con- 
sists of a series of colored bands. The different simple rays 
of which white light is composed are unequally refracted by 
the prism, and separate from each other on their emergence. 
The violet rays, which are farthest turned from their primitive 
direction, form the most deviated extremity of the spectrum. 
The red rays, wdiich are the least refracted, form the least de- 
viated extremity. The visible spectrum of solar light presents 
not only a succession of variously-colored bands ; when it is 
closely examined by the aid of magnifying instruments, it is 
found that the succession is not continuous, but that the lumi- 
nous bands are traversed by dark lines. These lines, which 
were discovered by Wollaston and studied by Fraunhofer, are 
very numerous, and are irregularly distributed throughout the 
spectrum, from the red to the violet, but each one of them 
occupies a definite position, and for the principal lines that 
position has been determined by exact measurements. Fraun- 



CESIUM AND RUBIDIUM. 301 

hofer designated tliem by the letters A, B, C, J), E, F, Gr, H. 
The D line is the most distinct of all : its place is in the yel- 
low. Other lights, the stars, for example, give similar discon- 
tinuous spectra. On the contrary, an incandescent platinum 
wire, or an}^ other luminous source which contains no volatile 
matter, gives a continuous spectrum. 

Very interesting facts are observed when the sources of light 
are flames into which the vapors of volatile substances, par- 
ticularly the metallic salts, are introduced. The spectra of such 
flames are formed exclusively of brilliant lines (see plate). 

If a platinum wire which has been dipped into a solution 
of sodium chloride be introduced into the colorless flame of 
a Bunsen burner, the flame will assume a yellow color, and will 
give a visible spectrum, but one which is very incomplete, 
since it consists of a single yellow line. It has been found 
that this line exactly coincides with the dark line D, existing in 
the yellow of the solar spectrum. This line characterizes 
sodium in all of its compounds : it is the spectrum of sodium. 

In the same manner, a flame into which a compound of potas- 
sium, lithium, barium, calcium, or other volatile metal is intro- 
duced, will give for each metal a particular spectrum formed of 
variously-colored lines. Each is perfectly characterized by the 
number, color, and position of the lines. Barium gives the most 
numerous and the widest lines ; other metals give more compli- 
cated spectra. That of iron is composed of 70 brilliant lines. 

Kirchhoff" and Bunsen, who discovered these facts, made a 
happy application of them to analysis. To detect the presence 
of a metal in a compound or even in a mixture, a small portion 
of the substance is introduced into a colorless gas flame, and 
the spectrum then given by the flame is observed by the aid of 
an instrument called a spectroscope. 

The method is so sensitive that -g-.-oo-J.-ro o" ^^ ^ milligramme 
of sodium chloride will render the yellow sodium line distinctly 
visible. The discovery of two new metals, caesium and rubi- 
dium, crowned the brilliant researches of Kirchhoff" and Bunsen. 

Since then, three other new metals have been discovered by 
the aid of spectrum analysis : thallium, which gives a green 
line, indium, which gives an indigo-blue line, and gallium, 
which gives two violet lines very close together. Thallium was 
discovered by Crookes and Lamy, indium by Reich and Bichter, 
and gallium, the discovery of which was most remarkable of 
all, by Lecoq de Boisbaudran. 

26 



302 ELEMENTS OF MODERN CHEMISTRY. 



THALLIUM. 

The beautiful green line given by this metal was first ob- 
served by William Crookes, who regarded it as characteristic 
of a new element. The honor of having isolated the latter 
and establishing its true character belongs to Lamy. 

Thallium is a heavy metal which resembles lead in certain 
of its properties. It melts at 200°; its density is 11.9. It 
forms an oxide, TPO; a crystallizable hydrate, TIOH, which 
is soluble in water and also caustic ; a monochloride, TlCl, and 
a moniodide, TIL These compounds relate it to the alkaline 
metals, but others, which include an oxide, Tl'-'O^ and a trichlo- 
ride, TICP, separate it from that class. Its principal com- 
pounds have been studied by Lamy and Willm. 



BARIUM 

Ba = 137 



Bunsen obtained barium by the electrolysis of fused barium 
chloride ; this metal is very avid of oxygen, and tarnishes 
rapidly. It decomposes cold water. 

Barium Oxide, or Baryta, BaO. — Barium oxide is obtained 
by calcining barium nitrate. Its nature was first recognized 
in 1808, by Davy, who decomposed it by the'voltaic current. 
It is a gray, porous substance, which unites energetically with 
water, producing a hissing noise and a great disengagement of 
steam, due to the elevation of temperature. The product of 
the reaction is a white hydrate, ordinarily known as caustic 
baryta. 

BaO + H^O --= Ba(0H)2 

Barium oxide. Barium hydrate. 

Barium hydrate is soluble in two parts of boiling water, and 
on cooling is in great part deposited in large tabular crystals, 
containing 8 molecules of water. The solution of barium hy- 
drate in water is called baryta water. 

Barium Dioxide, BaO'. — When dry oxygen is passed over 
barium oxide heated to dull redness, the gas is absorbed and a 
dioxide, BaO", is formed. It is a gray, porous mass, some- 
times greenish. It loses one atom of oxygen at a bright-red 
heat. When brought in contact with water, it combines with 



BARIUM SALTS. 303 

the latter quietly and without disengagement of heat, forming 
a pulverulent hydrate. 

When treated with sulphuric acid, barium dioxide disen- 
gages oxygen mixed with ozone. When its hydrate is intro- 
duced into hydrochloric acid, hydrogen dioxide is formed. 

Barium Sulphide, BaS. — This is obtained by reducing 
barium sulphate with charcoal. 

BaSO* + C* = BaS + 4C0 

Barium sulphate. Barium sulphide. 

The sulphate is reduced to fine powder, and is mixed with a 
certain quantity of flour or rosin. The mixture is then made 
into a paste with linseed oil, and shaped into little balls. These 
are calcined at a bright-red heat in a covered crucible, and a 
porous, gray mass is thus obtained which, when treated with 
boiling water, yields a solution which deposits hexagonal tables 
after filtration and cooling. These crystals do not present a 
very constant composition : it is a mixture of sulphide, sulphy- 
drate, and hydrate of barium. Their solution has a light-yel- 
low color. 

BARIUM SALTS. 

Barium Chloride, BaCP -f 2H'0. — This salt is obtained 
by saturating the solution of barium sulphide with hydrochloric 
acid. Hydrogen sulphide is disengaged ; the solution is boiled, 
filtered, and evaporated to crystallization. Barium chloride 
separates in quadrangular tables belonging to the type of the 
right rhombic prism. These crystals are inalterable in the air. 
100 parts of water at 18° dissolve 43.5 parts of barium chlo- 
ride, and 78 parts at 105.5°, the temperature of ebullition of 
the saturated solution (Gay-Lussac). Absolute alcohol dis- 
solves -^\^ of its weight of barium chloride. 

Barium Nitrate, Ba(NO'^)^ — Barium nitrate is prepared 
by decomposing barium sulphide or carbonate with dilute nitric 
acid, and filtering and evaporating the solution. 

It crystallizes in regular octahedra, or in cubo-octahedra. 
The crystals are transparent and unaltered in the air. One 
part of this salt requires for its solution 20 parts of water at 
0.12°; 5 parts of water at 15°; 2.8 parts at 106°, the tem- 
perature of ebullition (Glay-Lussac). When heated to redness, 
barium nitrate gives ofi" oxygen, nitrogen, and red vapors, 
leaving a residue of oxide, BaO. 



304 ELEMENTS OF MODERN CHEMISTRY. 

Barium Sulphate, BaSO*. — This sah is found abundantly 
in nature as lieavi/ spar^ and sometimes occurs in right rhom- 
bic crystals. It is entirely insoluble in water and acids,, with 
the exception of concentrated sulphuric acid. It is precipi- 
tated as a finely-divided, amorphous powder when sulphuric 
acid or a soluble sulphate is added to a solution, even very di- 
lute, of a salt of barium. 

Barium Carbonate, BaCO^. — Barium carbonate constitutes 
an amorphous, white powder, which is obtained by double de- 
composition on adding solution of sodium carbonate to a solu- 
tion of barium sulphide. Natural barium carbonate is an 
abundant mineral, and is found crystallized in right rhombic 
prisms; it is called ivitlierite. 

Characters of Barium Salts. — Barium salts are precipi- 
tated neither by hydrogen sulphide nor by ammonium sulphide. 
Sodium carbonate produces in them a white precipitate. Even 
when very dilute, the barium salts produce a white precipitate 
with sulphuric acid, which is insoluble in either cold or boiling 
nitric acid. 



STRONTIUM. 

Sr = 87.5 

The compounds of this metal present great analogies to those 
of barium. 

Strontium was discovered by Davy in 1808, but the metal 
was isolated by Bunsen and Matthiessen by the aid of a process 
similar to that which serves for the preparation of barium. 
Matthiessen describes it as a yellow metal, having a density of 
2.50-2.58, harder than lead, and decomposing cold water. 

Strontium forms two oxides, a monoxide, SrO, and a dioxide, 
SrOl 

Strontium chloride, SrCP, crystallizes in deliquescent needles 
which contain three molecules of water of crystallization. It 
is very soluble in water and slightly soluble in alcohol; the 
alcoholic solution burns with a red flame. 

Strontium nitrate, Sr(NO^)'^, which is prepared like barium 
nitrate, is deposited from its hot aqueous solution in anhydrous 
octahedra, and crystallizes at low temperatures in oblique rhom- 
bic tables containing 5 molecules of water of crystallization 
(Laurent). 

The carbonate of strontium, SrCO^ (strontianite), and the 



CALCIUM. 305 

sulphate^ SrSO'' (celestine), are found native. These two salts 
are insoluble in water, and are deposited as white precipitates 
on adding a soluble carbonate or sulphate to the solution of a 
strontium salt. Strontium sulphate is less insoluble, however, 
than barium sulphate. 



CALCIUM. 

Ca = 40 

Lime, which is universally known, is the oxide of a metal 
called calcium. According to Lies-Bodard and Jobin, calcium 
may be obtained by decomposing calcium iodide with sodium 
in an iron crucible. Matthiessen obtained it by decomposing 
fused calcium chloride by the voltaic current. 

Calcium has a yellow color when freshly filed, but it tarnishes 
rapidly in moist air and becomes covered with a grayish layer 
of hydrate. When heated upon platinum-foil, it takes fire and 
burns with a dazzling flame. It decomposes water at ordinary 
temperatures. 

OXIDE AND HYDEATE OF CALCIUM. 

Lime, or calcium oxide, CaO, is obtained by calcining the 
carbonate in peculiar furnaces, which are called lime-kilns. It 
occurs as large, compact, and hard grayish masses, which con- 
stitute quick-lime. 

It is infusible, even at the highest temperatures. When 
exposed to the air, it attracts moisture and carbonic acid, aug- 
ments in volume, and is finally converted into a white, powder, 
a mixture of calcium hydrate and carbonate. When lime is 
sprinkled with water, it absorbs the liquid without giving rise 
to any particular phenomenon ; but in a little while, the pieces 
saturated with water become hot, give off steam, and then they 
split and increase in volume. If enough water be used, the 
quick-lime will be converted into a white powder, which is 
called slaked lime; it is calcium hydrate. 

CaO 4- H^O = CaO^H'^ = Ca(0H)2 

When slaked lime is suspended in water, a white, creamy 
liquid is obtained that is called milk of lime. If this be fil- 
tered or allowed to settle, the clear, limpid liquid resulting will 
have an alkaline reaction, for it contains a small quantity of 

26* 



306 ELEMENTS OP MODERN CHEMISTRY. 

calcium hydrate in solution : it is lime-water. Calcium hydrate 
is more soluble in cold than in hot water. 

Employment of Lime in Constructions. — Lime is largely 
employed for building purposes in both ordinary and submarine 
constructions. The limestone which is used for the preparation 
of lime is rarely pure, and consequently the product of its cal- 
cination presents different qualities, according to the propor- 
tions of foreign matters which remain in the lime, and which 
consist of a small quantity of magnesia, oxide of iron, and 
especially clay. Fat limes are those produced by the calcina- 
tion of almost pure limestones ; they develop much heat, and 
swell up very much on slaking. Such lime forms an unctuous 
and binding paste with water, and forms ordinary mortar when 
mixed with sand. Impure limestones yield lean lime, contain- 
ing magnesia, oxide of iron, and clay. It is gray, and develops 
but little heat and increases but slightly in volume on slaking. 
The calcination of limestone containing from 10 to 30 per cent, 
of clay produces hydranllc lime. Such lime sets under water, 
that is, the mortar solidifies after a few days, and becomes very 
hard, even when immersed in water. On account of this curious 
property it is used in submarine constructions. Such lime is 
yellow ; slaking it produces but little heat, and scarcely any in- 
crease in volume. The hydraulic mortar formed by its mix- 
ture with sand will harden under water. Mortars possessing 
this property may also be prepared by mixing lime with baked 
argillaceous materials, such as powdered tiles, pottery, bricks, 
etc. Certain argillaceous rocks of volcanic origin, the pozzolana 
so abundant near Vesuvius, for example, yield an excellent 
hydraulic lime when mixed with fat lime. 

Cement is a variety of lime resulting from the calcination of 
limestones containing from 40 to 50 per cent, of slate. When 
mixed with water, such cement sets in a few minutes in a solid 
mass like plaster. Vicat has shown that the different varieties 
of hydraulic lime and cement can be prepared by properly 
calcining carbonate of lime, or chalk, with various proportions 
,of clay. According to him, ordinary mortar sets because the 
lime gradually absorbs carbonic acid gas from the air, forming 
'a carbonate which hardens and binds together the grains of 
sand. The hardening of hydraulic lime and mortar is due to 
another cause : the clay which they contain in the anhydrous 
state tends to become hydrated and to form a double silicate of 
calcium and aluminium, or a silicate and aluminate of calcium, 



CALCIUM CHLORIDE— CALCIUM NITRATE. 30*7 

insoluble compounds, which become very coherent on contact 
with water. 

CALCIUM CHLORIDE. 

CaCP 

This salt is prepared by dissolving white marble or chalk in 
hydrochloric acid. When the solution is concentrated it deposits 
large, six-sided prisms, containing 6 molecules of water of crys- 
tallization. They are very deliquescent and produce a depres- 
sion of temperature when they are dissolved in water. If they 
be mixed with their own weight of snow or powdered ice, a 
cold of — 45° may be produced. 

When they are heated, they melt in their water of crystalliza- 
tion, of which they lose 4 molecules at 200°, and the remainder 
at a red heat ; at the latter point the mass enters into igneous 
fusion. On cooling, the fused calcium chloride solidifies to a 
white, crystalline mass, in which form it is ordinarily employed 
for the desiccation of gases. 

Calcium chloride dissolves readily in alcohol. 

CALCIUM NITRATE. 

Ca(N03j2 _|_ 4H20 

This salt is formed naturally in the neighborhood of dwell- 
ings, in the soils of cellars, and in damp walls. It is contained 
in what are known as saltpetre materials ; it exists in certain 
spring and well waters. It may be made by saturating nitric 
acid with calcium carbonate. It is very soluble in water and 
in alcohol. It crystallizes with difficulty in six-sided, oblique 
rhombic prisms, which contain 4 molecules of water of crys- 
tallization : they are deliquescent. 

CALCIUM CARBONATE. 

(carbonate of lime.) 
CaC03 

Calcium carbonate is found in great abundance in nature, 
and under different forms. It exists crystallized as Iceland 
spar and aragonite ; the former crystallizes in colorless, trans- 
parent, and doubly refracting rhombohedra ; the latter in right 
rectangular prisms. 



308 ELEMENTS OF MODERN CHEMISTRY. 

Marble, the various limestones, and chalk, constitute other 
varieties of natural calcium carbonate. Pure water dissolves 
but feeble traces of this salt; water charged with carbonic 
acid dissolves a larger quantity, converting it into dicarbonate. 
It is in this state that it is contained in hard waters. 

Calcium carbonate may be prepared by double decomposition 
between solutions of sodium carbonate and calcium chloride. 
When heated to bright redness, it is completely decomposed 
into lime and carbonic anhydride. 



CALCIUM SULPHATE. 

CaSO* 

This salt exists in two states in nature : anhydrous, it con- 
stitutes the anlii/drite of mineralogists ; combined with two 
molecules of water of crystallization, it forms gyjisam or plas- 
ter stone. Gypsum sometimes occurs in lance-head-shaped 
crystals, grouped together ; they are divisible into thin, trans- 
parent layers, easily scratched by the finger-nail. Certain 
varieties of gypsum constitute alabaster. All the forms of 
hydrated calcium sulphate contain 21 per cent, of water. 

When heated to 80° in the air, or to 115° in closed vessels, 
the sulphate, CaSO* -|- 2H-0, abandons its water of crystalli- 
zation and is converted into the anhydrous sulphate. Between 
120 and 130°, this dehydration is rapid and complete. It is 
operated on the large scale in plaster furnaces. In this state 
calcium sulphate will readily recombine with its water of 
crystallization. If the plaster be calcined at too high a tem- 
perature it will not again become hydrated. 

If powdered plaster of Paris be mixed with enough water 
to form a creamy litjuid, it may be poured into a mould, and 
in a few minutes will harden to a compact mass, completely 
filling every cavity of the mould. In becoming hydrated, the 
particles of calcium sulphate assume the crystalline form and 
increase in volume. These properties render plaster of Paris 
valuable in building operations. 

It is also employed to a large extent in agriculture. 

Calcium sulphate is but slightly soluble in water. 1000 
parts of boiling water dissolve a little more than 2 parts of 
the salt; at 35° they dissolve 2.G4 parts; at 20°, 2.05 parts. 



CALCIUM HYPOCHLORITE. 



309 



CALCIUM HYPOCHLORITE. 

■ Ca(C10)2 

Calcium hypoclilorite exists in a product largely employed 
in the arts under the name of chloride of lime, and which is 
obtained by exposing well-hydrated lime to the action of chlo- 
rine ; it is a mixture of calcium chloride and calcium hypo- 
chlorite. 



4C1 



2CaO = CaCP + Ca(C10)2 



Calcium chloride. Calcium hypoclilorite. 



The operation is conducted by passing a current of chlorine 
over slaked lime placed in thin layers upon shelves arranged 
in the walls of masonry chambers. The chlorine is made in 
earthenware vessels, A (Fig. 101), heated in a water-bath; it 




Fig. 101. 



is washed in the jars D, and then conducted into the upper 
part of the chamber by the tube Gr. In order to insure the 
preservation of the chloride of lime, an excess of lime is always 
left in it. 



310 ELEMENTS OF MODERN CHEMISTRY. 

Chloride of lime is a powerful bleaching agent ; it owes this 
property to the calcium hypochlorite which it contains, and 
which is decomposed by the action of acids. 

If hydrochloric acid be added to a solution of chloride of 
lime, chlorine gas is at once disengaged with effervescence. 
The reaction may be conceived to take place in two phases. 
The hydrochloric acid acts upon the hypochlorite, forming 
hypochlorous acid. 

2HC1 + Ca(ClO)^ = CaCP + 2HC10 

Calcium hypochlorite. Calcium chloride. Hypochlorous acid. 

The hypochlorous acid thus set free then reacts with the 
calcium chloride, forming calcium hydrate and chlorine. 

CaCP + 2HC10 = Ca(OH/ + 2CP 

The calcium hydrate is in the presence of an excess of hy- 
drochloric acid, by which it is reconverted into calcium chlo- 
ride. The latter salt is thus continually decomposed and 
re-formed. 

Chloride of lime is also decomposed by less energetic acids, 
even by carbonic acid gas. 

When a solution of chloride of lime is boiled, the hypochlo- 
rite which it contains is converted into chlorate and chloride. 

3Ca(C10)'^ = Ca(C10'^)^ + 2CaCP 

Calcium hypochlorite. Calcium chlorate. 

Characters of Calcium Salts. — Calcium salts are not pre- 
cipitated either by hydrogen sulphide or ammonium sulphide. 
Sodium carbonate forms in them a white gelatinous precipitate. 
Sulphuric acid and the soluble sulphates produce a white pre- 
cipitate, if the calcium solutions be concentrated or only mod- 
erately dilute. Oxalic acid, or better, ammonium oxalate, 
produces a white precipitate of calcium oxalate, even in the 
most dilute solutions of calcium salts. 



MAaNESIUM. 

Mg =28 

Magnesium was discovered by Bussy. Matthiessen obtained 
it by decomposing fused magnesium chloride by electricity. 

Preparation. — Deville and Caron recommend the following 
process for the preparation of considerable quantities of mag- 



3IAGNESIUM OXIDE — MAGNESIUM CHLORIDE. 311 

nesium. A mixture of 600 grammes of anliydrous magnesium 
chloride, 100 grammes of sodium chloride, 100 grammes of 
calcium fluoride, and 100 grammes of sodium cut into small 
pieces is heated to redness in a covered crucible. The magne- 
sium chloride is reduced by the sodium, and the magnesium 
set free collects in little globules disseminated in the fused 
mass, which must be stirred with an iron rod. These little 
globules are removed from the scorise when cold, introduced 
into a charcoal boat, and heated to bright redness in a current 
of hydrogen. The magnesium volatilizes and condenses far- 
ther on in the tube ; it may then be fused with a flux consisting 
of magnesium chloride, sodium chloride, and calcium fluoride. 
The metal collects at the bottom of the crucible. 

Properties. — Magnesium has a density of 1.74 or 1.75. It 
fuses at 500°. It decomposes water at ordinary temperatures 
but slowly. It may readily be rolled into ribbon or drawn into 
wire. The wire is gTayish and not very brilliant. The end 
of a bundle of these wires may be heated in an alcohol lamp 
until they take fire, and the whole may then be plunged into a 
jar of oxygen. They burn with an incomparable splendor that 
the eye cannot support; at the same time the jar becomes filled 
with a white smoke, which condenses into a white powder, the 
product of the combustion ; it is magnesia, the oxide of mag- 
nesium. 

MAGNESIUM OXIDE, OR MAGNESIA. 

MgO 

This body is obtained by calcining white magnesia, or mag- 
nesium hydrocarbonate. It is a white, infusible, light, and 
insipid powder. It does not dissolve in water, but combines 
with that liquid forming a hydrate, Mg(OH)' = MgO.H'O. 
This hydrate slowly restores the blue color to reddened litmus- 
paper. 

Magnesium hydrate is precipitated when a solution of caustic 
potassa is added to the solution of a magnesium salt. 

Calcined magnesia is frequently employed in medicine. 

MAGNESIUM CHLOEIDE. 

MgCP 

This salt is known in the anhydrous state and crystallized. 
Anhydrous magnesium chloride is prepared by dissolving the 



312 ELEMENTS OF MODERN CHEMISTRY. 

carbonate in hydrochloric acid, adding ammonium chloride to 
the solution and evaporating to dryness. A double chloride of 
magnesium and ammonium is thus obtained which may be per- 
fectly dried ; the dry mass is introduced into a clay crucible and 
heated; the ammonium chloride volatilizes, while the magne- 
sium chloride remains, and solidifies on cooling to a colorless, 
pearly mass. 

It is very soluble in water, and when properly concentrated, 
the solution deposits deliquescent, prismatic crystals containing 
six molecules of water of crystallization. These crystals can- 
not be dehydrated, nor can their solution be evaporated to 
dryness, without decomposing the chloride by the action of the 
water; under these circumstances the magnesium chloride is 
converted into hydrochloric acid and magnesia. 

MgCP + H^O = 2HC1 + MgO 

MAGNESIUM CARBONATE. 

MgC03 

The anhydrous carbonate MgCO^ {giobertite^ magnesite) is 
found native, crystallized in rhombohedra, similar to those of 
calcium carbonate. Considerable deposits are also found of a 
double carbonate of magnesium and calcium, known as dolomite. 

When a boiling solution of magnesium sulphate is precipi- 
tated by an excess of sodium carbonate, carbonic acid gas is 
disengaged, and a precipitate is formed containing at the same 
time magnesium carbonate and magnesium hydrate (magnesium 
hy drocarbonate) . 

When this is dried, it constitutes the white magnesia of the 
pharmacies. 

MAGNESIUM SULPHATE. 
MgSO^ -f 7H20 

This salt exists in solution in sea-water and in certain purga- 
tive mineral waters, such as those of Sedlitz, in Bohemia, and 
Epsom, in England. Hence the names Sedlitz salt and Epsom 
salt, formerly given to this body. 

At S.tassfurth, it is found crystallized with one molecule of 
water (kieserife) and mixed with the anhydrous sulphate. 

It is deposited from the mother-liquors of salt-marshes when 
they are evaporated at the natural summer heat (Balard). 

When it separates at ordinary temperatures from an aqueous 



ALUMINIUM. 313 

solution that has been tolerably concentrated by heat, it crystal- 
lizes in transparent and colorless right rhombic prisms. At 
0°, it crystallizes with 12 molecules of water; at 30°, with 6 
molecules. 

Its taste is disagreeable, at the same time salty and bitter. 
When magnesium sulphate crystallized with 7 molecules of 
water is heated, it first melts in its water of crystallization, of 
which it loses 6 molecules. At 132°, it still retains one mole- 
cule, which it loses only at 210°. 

It is very soluble in water; 100 parts of water at 0° dis- 
solve 25.76 parts of the anhydrous sulphate, and 0.47816 
part for every additional degree (Gray-Lussac). 

Magnesium sulphate forms a double sulphate with potassium 
sulphate, K^SO*.MgSO* + QWO. 

Characters of Magnesium Salts. — They are precipitated 
by neither hydrogen sulphide nor ammonium sulphide. Sodium 
carbonate produces a white, flocculent precipitate. Potassium 
hydrate and ammonia form white precipitates, but ammonia 
will not precipitate magnesia from an acid solution or from one 
containing ammonium chloride. Sodium phosphate and ammonia 
together produce a granular precipitate of ammonio-magnesium 
phosphate. 

ALUMINIUM. 

Al ^ 27 5 

This metal long remained a chemical curiosity, and has only 
become common within a few years. It was discovered in 
1827 by Wohler, and in 1854, H. Saint-Claire Deville succeeded 
in producing it on the large scale. It is obtained by decom- 
posing aluminium and sodium double chloride by sodium. 

APCP,2NaCl + 3Na^ =:= 8NaCl + AP^ 

In the arts, a mixture of sodium, aluminium and sodium 
double chloride, and cryolite, is projected into a reverberatory 
furnace heated to bright redness. The cryolite acts as a flux : 
it is a double fluoride of sodium and aluminium, found native 
in Greenland. - 

Aluminium is a white metal, and has a somewhat bluish 
lustre when polished. It is ductile, malleable, very sonorous, 
and a good conductor of heat and electricity. It is as light as 
glass and porcelain, its density being only 2.56. 
o 27 



314 ELEMENTS OF MODERN CHEMISTRY. 

Aluminium is unaltered by the air, even by moist air. When 
heated in thin sheets in a current of oxygen, it burns and is 
converted into alumina. Nitric and sulphuric acids scarcely 
attack it. Hydrochloric acid dissolves it rapidly, disengaging 
hydrogen. It is immediately attacked by boiling solutions of 
potassium or sodium hydrates; hydrogen is disengaged and 
alkaline aluminates are formed. 



ALUMINIUM OXIDE, OH ALUMINA. 

Cortmdum, a very hard precious stone, consists of anhydrous 
alumina. It is named oriental ruhy when it has a red color ; 
sajyphire when it is blue, and oriental topaz when it has a 
yellow tint. Emery is a sort of opaque corundum ; it is gran- 
ular and colored by a small quantity of oxide of iron. 

When ammonium carbonate is added to a solution of alum, 
carbon dioxide is evolved, and a gelatinous precipitate of hy- 
drated alumina is formed. 

The precipitate dissolves readily in caustic potassa. When 
heated, it loses water and is converted into anhydrous alumina ; 
the latter is undecomposable by heat ; it fuses only in the flame 
of the oxy hydrogen blow-pipe. Glaudin has succeeded in pro- 
ducing fine precious stones that cannot be cut by the file, and 
at least as hard as rock-crystal, by melting Limoge emerald 
(anhydrous alumina) with various substances, such as sand, 
kaolin, talc, and lime, which are added as fluxes. 

Alumina cannot be reduced by charcoal at the highest tem- 
peratures ; it can only be reduced by the joint action of char- 
coal and chlorine ; aluminium chloride is then formed. 

ALUMINIUM CHLORIDE. 

APC16 

When a current of chlorine is, passed over an incandescent 
mixture of alumina and charcoal, aluminium chloride and' 
carbon monoxide are formed (Oersted). 

APO^ -1- 3C -f CP = SCO + APCP 

Aluminium chloride thus formed is a white, crystalline sub- 
stance, sometimes having a light-yellow color. It is fusible, and 



ALUMINIUM SULPHATE — ALUM. 315 

volatilizes in the air at a temperature little above 100°. When 
exposed to the air it gives off white fumes and attracts moist- 
ure. It dissolves in water with production of heat. 

A solution of aluminium chloride may be obtained by dis- 
solving gelatinous alumina in hydrochloric acid. When this 
solution is evaporated, it decomposes as soon as it attains a 
certain degree of concentration, disengaging hydrochloric acid, 
and leaving alumina. 

Aluminium chloride readily combines with sodium chloride, 
forming a double chloride, Ar^CP.2NaCl, fusible towards 200°. 

ALUMINIUM SULPHATE. 

A12(SO*)3 4- 18H20 

This is obtained in the arts by decomposing non-ferruginous 
clays with sulphuric acid. It crystallizes with difficulty in 
needles and in thin, pearly scales. In this state it contains 18 
molecules of water of crystallization. It dissolves in 2 parts 
of cold water. When heated, it first loses its water, and at a 
higher temperature it gives off sulphuric anhydride, leaving a 
residue of alumina. 

AP(SO0' = 3S0^ + APO^ 

It is seen that aluminium sulphate represents 3 molecules 
of sulphuric acid, in which the 6 atoms of hydrogen have been 
replaced by the hexatomic couple AP. 

(SO* 
+ APO^ = 3H^0 -f- ( AP;- \ SO* 

ffso*) (so* 



H^SOn 



ALUMINIUM AND POTASSIUM DOUBLE SUL- 
PHATE, OR ALUM. 

A12(SO*)3.K2S04 -f 24H20 

If a concentrated solution of aluminium sulphate be added 
to a concentrated solution of potassium sulphate, and the mix- 
ture be stirred with a glass rod, a crystalline deposit soon forms 
from the union of the two salts to form a double sulphate 
which is alum. 

This salt is not very soluble in cold water, but dissolves 
abundantly in boiling water, and is deposited on cooling in 



316 ELEMENTS OF MODERN CHEMISTRY. 

voluminous, transparent octaliedra. When heated, these crys- 
tals melt in their water of crystallization (2-J: molecules), and 
in losing this water, the melted mass swells up considerably. 
Alum may be obtained crystallized in cubes, and it is prepared 
in this form in the neighborhood of Civita-Vecchia by working 
a mineral which contains the elements of alum with a large 
excess of alumina. The mineral is known as alummite, and the 
cubical alum is called Roman alum. 

This cubical variety may be prepared in the laboratory by 
adding a small quantity of potassium carbonate to a hot solu- 
tion of ordinary alum, so that the precipitate first formed will 
be redissolved on agitating the liquid. On cooling, cubical 
crystals are deposited which are ordinarily opaque. These are 
formed under the influence of a small quantity of basic sul- 
phate (aluminium sulphate combined with an excess of alu- 
mina) contained in the liquid, and which probably enters into 
the constitution of the crystals. With this slight difference, 
octahedral alum and cubical alum present the same composi- 
tion, which is expressed by the formula AP(SO*)lK'SO* + 
24ffO. 

Ammonia alum is obtained by adding ammonium sulphate 
to solution of aluminium sulphate. It possesses a constitution 
analogous to that of ordinary alum, with which it is isomor- 
phous. It contains 

AP(SO^)l(NH*)'SO^ + 24.WO 

It is often substituted in the arts for potassium alum, being 
cheaper than the latter. 

When strongly calcined, it leaves a residue of pure alumina. 

Other alums are known in which iron, manganese, and chro- 
mium play the part taken by aluminium in ordinary alum. 
These alums are all isomorphous (Mitscherlich). By the ac- 
tion of sulphuric acid on the sesquioxides of the above metals, 
sulphates are formed analogous to aluminium sulphate, and of 
which the composition is expressed by the general formula 
(IlO''(SO*)l With the sulphates M^SO*, they form alums, all 
of which crystallize in regular octahedra, and which can be 
mixed in one and the same crystal without the form of the 
latter being affected by the mixture. 

The following are the most important of these compounds : 

Manganese alum .... Mn2(SOi)3.K2SO^ + 24H20 

Iron alum Fe2(S04)3.K2SO* + 24H20 

Chromium alum .... Cx\^O^f,^^^0^ + 24H20 



ALUM. 317 

It is seen that eacli of these presents an atomic composition 
similar to that of ordinary alum. 



o 



The aluminium compounds are widely disseminated in nature. 
Feldspar is a double silicate of aluminium and potassium. The 
latter metal is replaced by sodium in alhite^ and by calcium in 
lahradorite. 

Many other minerals contain aluminium silicate combined 
with alkaline or earthy silicates : such are granite^ idiocrase^ 
mica^ etc. The zeolites are silicates of aluminium containing 
water of crystallization. 

Clay is a hydrated silicate of aluminium ; it results from the 
disintegration of feldspar by the action of water and air, the 
alkaline silicate being gradually dissolved and eliminated. The 
purest clay is kaolin^ or porcelain clay; it contains alumina, 
silica, and water in the proportions indicated by the formula 
2SiO^,AP0^2H^O. 

Plastic clays are those which form a binding paste when 
mixed with water, and acquire great hardness after being 
baked, without fusing. They are used for the manufacture of 
pottery, refractory fire-bricks, and crucibles. Fuller s earth is 
a clay which forms with water a paste that is but slightly adhe- 
rent ; it is employed in scouring and fulling cloth. 

Marls are intimate mixtures of clay and chalk ; they are 
employed in agTiculture. 

Pottery. — Clay is the basis of all pottery. Other matters, 
such as sand, powdered feldspar or quartz, etc., are generally 
added, for while they diminish the plasticity of the clay, they 
also diminish its shrinkage on baking. Pottery is classified as 
semivitrified pottery, such as porcelain and stoneware ; porous 
pottery, such as faience and bisque ; and common pottery or 
terra-cotta. 

Porcelains. — These are manufactured from kaolin, to which 
sand is added to prevent shrinkage, and feldspar, which causes 
the ware to undergo a partial fusion, and renders it translucent. 
These materials are finely pulverized, mixed with water, and 
the paste is kneaded for a long time in order to render it homo- 
geneous. Pieces fashioned in this paste are submitted to a pre- 
liminary baking, which gives them a certain degree of coherence. 
The porous porcelain thus obtained must be coated with a var- 
nish which will melt and spread upon its surface : this glaze is 

27- 



318 ELEMENTS OP MODERN CHEMISTRY. 

formed of a mixture of quartz and kaolin reduced to an impal- 
pable powder ; the latter is suspended in water, into wliicli the 
pieces are dipped. They are then subjected to a second baking 
in ovens where the temperature is sufficiently elevated to fuse 
the glaze and partially vitrify the paste. 

Ceramic Sto7iewares. — These are manufactured from the 
same materials as porcelain, but less pure ; they are therefore 
slightly colored. They are baked at a high temperature, and 
are glazed by throwing common salt upon the incandescent 
objects in the furnace ; hydrochloric acid is disengaged, and ti. 
double silicate of aluminium and sodium is formed, which fuses 
and spreads upon the surface of the ware. 

Faiences are made from plastic clay mixed with quartz re- 
duced to an impalpable powder. Articles formed of this paste 
are submitted to a preliminary baking, and are then coated with 
a fusible glaze, composed of quartz, potassium carbonate, and 
oxide of lead. A second baking causes the pieces to become 
covered with an impermeable, vitreous layer of silicate of lead 
and potassium. This glaze is transparent ; for ordinary ware 
it is rendered opaque by the addition of oxide of tin. It is 
a true enamel. 

Common pottery, which serves for culinary purposes, is made 
from ferruginous clay, mixed with sand and marl. The glazing 
is composed of a double silicate of aluminium and lead. 



IRON.- 

re(Ferrum) = 56 

Natural State and Metallurgy.— Iron is the most impor- 
tant of the metals. Its preparation and working are difficult, 
therefore it was not the first metal used by civilized man. The 
bronze age preceded the iron age, and those who first employed 
the latter metal probably extracted it from the masses which 
fall from time to time upon the surface of the earth, and are 
known as meteorites. Their principal constituent is metallic 
iron, which is alloyed with nickel, cobalt, and chromium. 

Iron is employed in three principal forms : soft or malleable 
iron, cast iron, and steel. Soft iron is almost pure iron ; cast 
iron is a combination of iron with carbon and silicon ; steel 
also contains carbon, but in smaller proportion than cast iron. 

The principal ores of iron are the magnetic, or black oxide, 



IRON. 



319 



Fe^O*, red hematite, Fe'^O^, and spathic iron or ferrous carbon- 
ate, FeCO^. The various hydrates of the sesquioxide (^oolitic 
iron^ brown hematite^ etc.) and ferrous carbonate mixed with 
clay (bog-iron ore), are more abundant than the preceding, but 
are not as rich and are less valuable. 

All of these minerals are oxidized. If the ore contain sul- 
phur, that element is first driven out by roasting. The metal- 
lurgy of iron then consists in reducing the oxide with carbon, 
and separating the reduced iron from the earthy matter, which 
is generally silicious. Two methods are employed for this 
purpose. The first consists in heating the rich ores with 
charcoal alone ; part of the oxide of iron then combines with 
the gangue, forming a very fusible slag (double silicate of 
aluminium and iron). This is the Catalan method. The 
other consists in mixing the ore with, coal and calcium carbon- 
ate ; the gangue then com- 
bines with the lime, forming 
a double silicate of lime and 
aluminium, which fuses only 
at a very high temperature. 
Under these conditions the 
iron unites with a portion 
of the carbon, forming cast 
iron. This is the blast- fur- 
nace method. 

Catalan Method. — This is 
only applicable to very rich 
ores and in countries where 
combustibles are expensive, 
as in Spain, the Pyrenees, 
and in Corsica. 

Fig. 102 represents a sec- 
tion of a Catalan furnace ; it 
is a trough-shaped masonry 
furnace with a hearth. The 
materials are placed in two 
piles, side by side, upon a layer of well-ignited charcoal ; one pile 
consists of charcoal and is next the tuyere ; the other is the 
ore, equal to half the quantity of charcoal, and is placed oppo- 
site. The combustion is sustained by the blast from a tuyere, 
D, which reaches the border of the hearth. The carbon 
dioxide here formed is converted into carbon monoxide by the 




Fig. 102. 



320 



ELEMENTS OP MODERN CHEMISTRY. 



mass of incandescent charcoal, and the latter gas reduces the 
ore, again passing into the state of dioxide. Metallic iron is 
thus formed, and at the same time a- portion of the ferric 
oxide is reduced to ferrous oxide, and combines with the 
gangue, forming a double, alumino-ferrous silicate, which is very 
fusible and constitutes the slag. The reduced iron collects in 
the bottom of the hearth in the form of a spongy mass, which 
is agglutinated and forged under the hammer. 




Fig. 103. 



Blast-furnace Process. — All iron ores may be treated by this 
method. They are crushed and introduced with alternate 
layers of limestone and coal into the blast-furnace (Fig. 103). 
The latter has the form of two cones, the bases of vv^hich are 



IRON. 321 

joined together. It is closed at the bottom, and hot air is in- 
jected through tuyeres to .sustain the combustion. It is open at 
the top, where it is continually charged with fresh materials, as 
the incandescent mass sinks in the furnace and the molten mate- 
rials are drawn off below. The latter first collect in a cavity 
placed below the vent of the tuyere, and separate on this 
hearth into metal, which sinks to the bottom, and slag, which 
floats and flows over the edge. When the crucible is full of 
molten metal, the latter is run off into channels made in sand 
upon the floor of the casting-room. In these rough moulds it 
solidifies in bars having a semicircular section, which are called 
pigs. 

The reactions which take place in the blast-furnace are of 
great interest. At the lower part, where the temperature is 
the highest, carbon dioxide is produced by the combustion of 
the coal ; farther up, in the widest portion, this gas is reduced 
to carbon monoxide by the incandescent coal ; still higher, 
where the furnace begins again to contract, and where the 
temperature is dull red, the carbon monoxide reduces the oxide 
of iron, and a spongy mass of metallic iron is there formed. 

In descending, this iron unites with part of the carbon, and 
at the same time the silica of the gangue combines wdth the 
lime, forming a silicate which fuses and constitutes the slag. 

A small quantity of silica is reduced in the hottest part of 
the furnace, and the silicon formed combines with the cast iron. 

Cast iron is converted into soft iron by refining ; this opera- 
tion consists in removing from the cast iron the greater part 
of its carbon. For this purpose it is melted in contact with 
the air ; the carbon, silicon, and a small proportion of iron are 
oxidized, forming a basic silicate, of which the excess of oxide 
is finally reduced by the carbon of the cast iron. The latter 
thus becomes less fusible, and is converted into a spongy mass 
of soft iron. Several of these masses are united and the scoriae 
expressed from them by the blows of a steam-hammer. Or the 
metal is melted on the hearth of a reverberatory furnace under 
a layer of ferruginous scoriae and scales of oxide of iron ; the 
oxygen of these materials burns the carbon out of the cast iron, 
the whole mass being vigorously stirred. The latter operation 
is called puddling. 

Preparatio)i of Pure Iron. — Pure iron may be obtained by 
reducing ferric oxide by hydrogen at a temperature near red- 
ness, or by passing hydrogen over anhydrous ferrous chloride 
o* 



322 ELEMENTS OF MODERN CHEMISTRY. 

contained in an incandescent porcelain tube. Hydrocliloric 
acid is formed and evolved, and the iron remains as a gray, 
spongy mass, having a metallic lustre where it has been in 
contact with the porcelain (Peligot). 

Properties of Soft Iron. — Forged, or bar iron, is not chem- 
ically pure. It contains a small quantity of carbon, and traces 
of silicon, sulphur, and phosphorus, and even nitrogen. The 
purest soft iron is that used for the teeth of carding-machines 
and for piano-strings. 

The density of forged iron varies from 7.4 to 7.9. It is 
very tenacious, ductile, and malleable. When rolled out, it is 
called sheet iron. Tin plate is sheet iron covered with a layer 
of tin. Gralvanized iron is coated with a surface of zinc. 

Iron melts only at the highest heats of a wind-furnace. 
When softened by a white heat, it may be soldered to itself, or 
welded, a very important property for the working of the metal. 

Iron is attracted by the magnet ; it is magnetic ; but it is 
not, like steel, capable of retaining magnetism when removed 
from the magnetic influence. 

It is not altered by dry air at ordinary temperatures, but at 
a red heat it absorbs oxygen and is converted into scales of 
black oxide of iron. 

Iron may be obtained as an impalpable powder by reducing 
finely-divided ferric oxide by a current of hydrogen at as low a 
temperature as possible. In this state it takes fire when ex- 
posed to the air at ordinary temperatures : it is pyroplioi-ic. 

Iron rapidly becomes oxidized in moist air ; it becomes cov- 
ered with a layer of rust, which is ferric hydrate. It is con- 
sidered that the oxidation of iron moistened with water is first 
set up by the oxygen dissolved in the water; it continues 
with greater energy as soon as a light coat of ferric hydrate 
has been forntfed on the metal. The hydrate forms a voltaic 
couple with the iron itself, by which the water is decomposed ; 
part of the hydrogen displaced by the iron combines with the 
nitrogen of the air, forming ammonia; indeed, rust always 
contains a small proportion of ammonia. 

Iron decomposes water at a red heat, setting free the hydro- 
gen. It dissolves readily in hydrochloric acid, liberating impure 
and fetid hydrogen. Its oxidation by nitric acid is attended 
by curious phenomena. 

If dilute nitric acid be poured upon iron tacks, the metal is 
at once attacked with an abundant disengagement of red vapors. 



IRON. 323 

On the other hand, the same metal is not attacked by very 
concentrated nitric acid (monohydrated), and after having been 
exposed to the strong acid, the tacks may be put into dilute acid, 
and the latter will then be found to have no effect. 

By the action of the concentrated acid, the iron becomes 
passive; its surface is covered with a thin layer of gas which 
protects it. But if it be touched at any point with a copper 
wire while in the dilute acid, chemical action will instantly be 
re-established. 

Cast Iron and Steel. — The properties and appearance of cast 
iron differ with the proportions of carbon and silicon which it 
contains. The iron does not form definite compounds with 
these bodies; they seem to be dissolved by the cast iron when 
it is liquid. When cast iron containing much carbon is quickly 
cooled, it becomes hard, brittle, whiter than soft iron, and seems 
homogeneous. This is white iron. When slowly cooled, a large 
proportion of the carbon is deposited as laminas of graphite, 
and the less homogeneous iron then possesses a certain degree 
of malleability : it is gray iron. 

Some cast irons contain traces of sulphur and phosphorus; 
they remain white even after very slow cooling. Others are 
lamellar and glittering; they contain manganese and are rich 
in carbon. 

The proportion of carbon contained in cast iron varies from 
2 to 5.5 per cent. Steel contains less carbon, from 0.7 to 2 
per cent. The quantities of carbon contained in steel and even 
in cast iron render it difficult to suppose that these products 
are veritable carbides of iron. 

Steel may be obtained by a partial decarbonization of cast 
iron. Manganiferous iron is especially applicable for this prep- 
aration. It is submitted to a partial refining, being maintained 
in the liquid state for some hours under a layer of scoriae rich 
in oxide of iron. A part of the carbon is burned out by the 
oxygen of this oxide : natural steel is thus obtained. 

Soft iron may be converted into steel. The operation is con- 
ducted in cases of refractory fire-clay, into which bars of iron, 
and charcoal-powder, mixed with a small quantity of ashes and 
common salt, are introduced in alternate layers. The bars being 
thus isolated in a bed of charcoal, the cases are closed and 
heated to redness in a furnace. The incandescent metal absorbs 
carbon, and at the termination of the operation is found con- 
verted into steel by cementation. 



324 ELEMENTS OF MODERN CHEMISTRY. 

The most liomogencous and most valuable steel is cast steel. 
It is obtained by fusing crude steel in crucibles in a wind-fur- 
nace. 

Bessemer has introduced an important improvement in the 
manufacture of steel. His process, which bears his name, con- 
sists in adding variable quantities of a properly-constituted cast 
iron to molten and perfectly refined soft iron. 

In this process, the iron to be converted into steel is decar- 
bonized by a current of air which is forced through the molten 

metal by strong press- 
ure. The operation is 
conducted in an appa- 
ratus represented in 
Fig. 104, which is 
called the converter. It 
has an ovoid form, is 
constructed of strong 
plate iron, and is well- 
lined with refractory 
fire-bricks. It is ar- 
ranged on trunnions, so 
that an oscillating move- 
ment may be given to it. 
The air arrives under 
pressure by the tuyeres 
which open into the bot- 
tom of the converter. 
2Q^ The latter is first filled 

with incandescent coke, 
which is brought into active combustion by the blast. When 
the interior of the converter is heated to whiteness, the coke 
is emptied out and replaced by the molten cast iron, the con- 
verter being inclined to prevent the entrance of the metal into 
the tuyeres. The blast is then again turned on, and the com- 
pressed air bubbling through the molten metal burns out all 
of the carbon. A flame of great brilliancy rushes from the 
orifice of the apparatus, and the aspect of this flame indicates 
precisely the progress of the operation and its termination. 
At this moment the apparatus is inclined, the blast arrested, 
and a sufficient quantity of melted cast iron or spiegdeiscn^ a 
crystalline cast iron rich in carbon, is added to the now refined 
iron to convert the whole into steel ; about 7 per cent, of spie- 




OXIDES OF IRON. 325 

geleisen is required. The steel is then run out into suitable 
moulds. 

The valuable qualities of steel are well known. It is suscep- 
tible of a high polish ; it is ductile and malleable like iron, and 
can also be forged. At the temperature at which malleable 
iron becomes soft, steel melts. It becomes hard and brittle 
when it is suddenly cooled after having been heated to redness. 
This operation, which is called tempering, develops new quali- 
ties in the steel, — elasticity and hardness. It assumes these 
properties in different degrees, according to the rapidity of the 
cooling, and the difference between the temperature to which 
it has been heated and that to which it is cooled. The greater 
this difference, and the more rapid the cooling, the harder will 
the steel become. After a slow cooling, it is soft and mallea- 
ble like iron. 

When tempered steel is heated, and allowed to cool slowly, 
it partly or entirely loses its hardness. It loses it entirely if 
it t)e heated to the temperature to which it was exposed before 
tempering. Its temper is drawn incompletely, that is, it re- 
tains a certain amount of hardness and elasticity, if it be re- 
heated to inferior temperatures. The qualities which it will 
assume after cooling may be predicted from the various tints 
developed on its surface during the heating. Each of these 
tints corresponds to a determined temperature. 

Straw-yellow corresponds to 220° 
Brown " 255° 

Light blue « 285-290° 

Indigo-blue " 295° 

Sea-green " 331° 

OXIDES OF IRON. 

Three oxides of iron are known: 

Ferrous oxide FeO 

Ferric oxide Fe^Qs 

Ferroso-ferric oxide Fe^O* 

Fremy has also discovered the existence of a ferric acid, of 
which the composition is not certainly established. 

Ferrous Oxide, FeO. — Debray has obtained this oxide by 
partially reducing ferric oxide. The latter is heated in a cur- 
rent of gas formed of equal volumes of carbon monoxide and 
carbon dioxide. A black powder remains, which is ferrous 
oxide. 

Fe^O' + CO = 2FeO -|- CO^ 
28 



32G ELEMENTS OF MODERN CHEMISTRY. 

Ferric Oxide, Fe^Ol — This is found anhydrous in nature 
in red hematite and specular iron. It may be prepared by 
calcining ferrous sulphate, or green vitriol. This salt first 
loses its water, and then at a red heat decomposes into sul- 
phuric anhydride, sulphurous oxide, and ferric oxide. 

2FeS0* = SO'^ + SO' + Fe'O^ 

A red powder is thus obtained, which is known as colcothar, 
or jeweller's rouge. 

This oxide is amorphous, while red hematite is crystallized in 
acute rhombohedra. H. Deville has succeeded in converting 
the amorphous oxide into the crystallized by heating the former 
to redness in a very slow current of hydrochloric acid. 

Rust is ferric hydrate, a combination of ferric oxide with 
water, and ordinarily presents the composition 

2Fe'0^ + 3H'0 

Such a hydrate is also encountered in nature as brown 
hematite. Another natural hydrate, containing Fe'^0^ -j- H'O, 
is known under the name of goethite. 

Ammonia or potassium hydrate will at once produce a volu- 
minous and flocculent, rust-colored precipitate in a solution of 
ferric chloride. This precipitate constitutes a ferric hydrate. 

But if an excess of tartaric acid be added to the solution of 
a ferric salt, the liquid may be saturated with potassium hy- 
drate and will still remain clear, no precipitate of ferric hydrate 
being formed. 

Advantage is taken of this property in analysis for the sepa- 
ration of ferric oxide from other oxides which tartaric acid does 
not retain in solution in an alkaline liquid. 

If a solution of ferric acetate be poured into a dialyser 
(page 199), and the water in the exterior vessel be frequently 
changed, the salt will finally be entirely decomposed. Acetic 
acid will pass through the membrane, while ferric hydrate will 
remain dissolved in the water in the dialyser (Graham). 

Ferroso-ferric Oxide, Fe'^0*. — This compound, also called 
magnetic oxide of iron, constitutes the black scales which form 
upon the surface of iron when it is heated to redness in the 
air ; it may be regarded as a compound of ferrous and ferric 
oxides. FeO 4- Fe'O^^ = Fe^^OV 



SULPHIDES OF IRON — ^CHLORIDES OF IRON. 321 



SULPHIDES OF IRON. 

Several sulphides of iron are known. 

The disulphide, or pyrites, FeS^ a largely-diffused mineral, 
is the most important of these sulphides. It occurs in two 
distinct forms : 

Yellow pyrites^ which crystallizes in cubes. It occurs as 
brilliant cubes, or dodecahedra, having a yellow color and a 
metallic lustre. 

White pyrites, which forms rhombic prisms, variously modi- 
fied, and presents a dull, greenish-yellow color. This variety 
is much more alterable than the other, and possesses a great 
tendency to attract oxygen from the air arid become converted 
into sulphate. When heated in closed vessels, pyrites loses a 
part of its sulphur. 

A combination of monosulphide and sesquisulphide of iron 
is encountered in nature ; it crystallizes in regular hexagonal 
prisms and is called magnetic jiy rites. 

Monosulphide of Iron, FeS, is found in small quantity in 
many meteorites. It is ordinarily obtained by heating to red- 
ness in a covered crucible a mixture of three parts of iron- 
filings and two parts of sulphur. When the mixture has 
fused, it is poured out and solidifies to a brittle, blackish mass, 
having a metallic reflection. In this state, it is used for the 
preparation of hydrogen sulphide. 



CHLORIDES OF IRON. 

Ferrous Chloride, FeCP, is obtained anhydrous by the action 
of dry hydrochloric acid gas upon metallic iron. It forms white 
pearly scales. When iron is treated with aqueous hydrochloric 
acid, it dissolves, and hydrogen is disengaged. The green, 
filtered liquid deposits, when sufficiently concentrated, bluish- 
green, oblique rhombic prisms. This is hydrated ferrous chlo- 
ride, FeCP -f 4ff 0. 

Ferric Chloride, Fe^CP, is formed when a current of chlorine 
is passed over iron-turnings heated in a glass or porcelain tube. 
The two bodies combine with incandescence, and if the chlorine 
be in excess, ferric chloride will be obtained as a brilliant black, 
crystalline sublimate. 



328 ELEMENTS OF MODERN CHExMISTRY. 

This body is very soluble in water and forms a yellow-brown 
solution. The latter may be obtained by dissolving ferric oxide, 
such as powdered hematite, in hot hydrochloric acid, or by 
passing chlorine into a solution of ferrous chloride. Ferric 
<ihloride is also soluble in alcohol. 

FERKOUS SULPHATE. 

FeSO* + 7H20 

This salt has long been known under the names green 
vitriol and copperas. It is obtained by exposing iron pyrites 
to the air, or roasting that mineral at a moderate heat. It is 
generally prepared by dissolving iron in dilute sulphuric acid, 
and it is a residue from the preparation of hydrogen sulphide 
by means of iron sulphide and dilute sulphuric acid. 

It crystallizes in oblique rhombic prisms, containing 7 mol- 
ecules of water of crystallization. AVhen exposed to the air, 
these crystals effloresce slightly, and at the same time their 
surface becomes yellow from absorption of oxygen and the 
formation of ferric subsulphate. 

2FeS0^ + == Fe-0(SO*)' == Fe^0l2S0'^ 

When heated, they lose their water, of which six molecules 
are disengaged at 114°, and the seventh only at 300°. At a 
higher temperature the salt decomposes into sulphurous oxide, 
and a ferric subsulphate different from the preceding. 
2FeS0* = SO^ + (Fe^O^)SO* 

The crystals of ferrous sulphate are freely soluble in water. 
100 parts of the salt dissolve in 1G4 parts of water at 10°, and 
in 30 parts of boiling water. The green solution absorbs oxy- 
gen from the air, becomes troubled, and deposits yellow ferric 
subsulphate. 

Other hydrates of ferrous sulphate are known. According 
to Mitscherlich, a saturated boiling solution of the salt deposits 
at 80° crystals containing four molecules of water. According 
to Marignac, when a solution of ferrous sulphate containing 
free sulphuric acid is evaporated in a vacuum, crystals are first 
deposited which contain 7 molecules of water, then a sulphate 
FeSO* + 5H'0, and finally, FeSO -|- 4H'0. 

The sulphate FeSO* + 5H'-0, is isomorphous with crystal 
lized cupric sulphate (blue vitriol), and like it crystallizes in 
dissymetric prisms. 



FERRIC SULPHATE — FERROUS CARBONATE. 329 

FEURIC SULPHATE. 

Fe2(SO*)5 

This salt is obtained by heating ferrous sulphate with nitric 
and sulphuric acids; the brown solution is evaporated, and the 
residue well dried. 

2FeS0^ + ff SO* + = WO + Fe\SO*/ 

Ferric sulphate is a slightly -yellowish, white mass, which 
dissolves completely, but very slowly, in water. The solution 
is yellow-brown, and has an acid reaction. 

When concentrated by evaporation, it deposits a deliquescent, 
yellowish, crystalline mass, which constitutes hydrated ferric 
sulphate. 

There are several ferric suhsulphates ; those which have 
been mentioned above result from the action of one molecule 
of ferric oxide upon one or two molecules of sulphuric acid, 
the neutral sulphate resulting from the action of one molecule 
of ferric oxide upon three molecules of sulphuric acid. 

H^SO* + Fe^O^ = WO + (Fe^O^)"SO* 

Ferric monosulphate. 



g|g; + Fe^03 


= 2IP0+ (Fe^Ofj^^l 


H^SO* 

H^SO* + Fe^O^ = 

H^SO* 


Ferric disulphate. 

(SO* 

. 3H^0 + (Fe^)- -l SO* 

(SO* 

Ferric trisulphate (normal sulphate). 



FERROUS CARBONATE. 

FeC03 

Spathic iron ore^ which crystallizes in rhombohedra, is fer- 
rous carbonate. When a solution of sodium carbonate is added 
to a solution of ferrous sulphate, a greenish-white precipitate 
is obtained, which rapidly becomes colored in the air, absorb- 
ing oxygen and losing carbonic acid. When recently precipi- 
tated, it dissolves in a large excess of carbonic acid. 

Characters of Ferrous Salts. — The solutions of these salts 
are green ; they are not precipitated by hydrogen sulphide, but 
ammonium sulphide forms a black precipitate of ferrous sul- 

28- 



330 ELEMENTS OF MODERN CHEMISTRY. 

pliide. Potassium hydrate or ammonia produces a greenish- 
white precipitate of ferrous hydrate, insoluble in an excess of 
the reagent, and rapidly becoming colored in the air. Potas- 
sium ferrocyanide (yellow prussiate of potash) forms with fer- 
rous salts a light-blue precipitate. Potassium ferricyanide (red 
prussiate) forms a dark-blue precipitate. Solution of gall-nuts 
does not color ferrous salts. 

Characters of Ferric Salts. — Hydrogen sulphide produces 
a precipitate of sulphur, reducing the salts to the ferrous state. 
Ammonium sulphide precipitates them black. Potassium hy- 
drate and ammonia form red-brown precipitates of ferric hy- 
drate, insoluble in an excess of the reagent. Potassium ferro- 
cyanide forms a dark-blue precipitate which is Prussian blue. 

Potassium ferricyanide produces a dark-brown color without 
precipitation. Potassium sulphocyanate gives a blood-red color. 

Solution of gall-nuts forms a bluish-black precipitate which 
constitutes ink. 

ZINC. 

Zn = 65.2 

Treatment of Zinc Ores. — The zinc ores which are worked 
are calamine and blende. Calamine is carbonate of zinc, often 
mixed with silicate ; it contains also oxide of iron. Blende is 
sulphide of zinc; it frequently contains a small quantity of 
ferrous sulphide, which gives it a brown color, more or less 
intense. 

Zinc ores are abundant in England, Silesia, Belgium, and 
throughout the United States. They are generally accom- 
panied by other minerals; thus, blende is often mixed with 
pyrites and galena (lead sulphide). The ore is then first sub- 
mitted to an ingenious system of washing, by which the various 
sulphides separate from each other by reason of their different 
densities. 

In order to extract the zinc from blende separated by this 
method, or from calamine, the minerals are first roasted. By 
the action of heat calamine loses carbonic acid gas and water, 
and the blende disengages sulphurous oxide and is converted 
into zinc oxide. Thus converted into oxide, and rendered more 
friable by the heat, the zinc ores are pulverized and calcined 
with charcoal. Carbon monoxide is disengaged, and the zinc 
set at liberty volatilizes, and is condensed in suitable recipients. 



ZINC. 



331 



The operation is conducted in cylinders of refractory clay, a 
number of which are arranged in a furnace, and their open 
extremities connected with conical recipients of galvanized iron 
(Fig. 105). In Silesia, these cylindrical retorts are replaced by 
muffles, which are heated in a furnace and communicate with 
recipients placed outside (Fig. 106). 




Fig. 105. 



Fig. 106. 



In England, the reduction of the roasted ore is accomplished 
in crucibles, through the bottoms of which pass vertical tubes 
which terminate in a reservoir below the furnace. The zinc 
vapors first rise and then descend by 
the tube, and as they condense, the 
melted metal flows into the recipient. 
The operation is called distillation per 
descemum (Fig. 107). 

The zinc of commerce is not always 
pure, especially when it occurs in 
masses ; it contains small quantities of 
iron, copper, lead, cadmium, carbon, 
and arsenic. Sheet zinc is generally 
less impure. Zinc may be purified 
by melting it several times with small 
quantities of nitre. 

Properties. — Zinc has a bluish- 
white color; its density varies from 6.86 to 7.2, according as 




332 ELEMENTS OF MODERN CHEMISTRY. 

it has been melted or rolled; its fracture is laminated and bril- 
liant. Commercial zinc is brittle at ordinary temperatures ; it 
becomes malleable at a few degrees above 0"^, but when heated 
to 200° it again becomes brittle. It melts at -ilO°, and distils 
at about 1000° (H. Deville and Troost). Its surface soon 
tarnishes in moist air, but the oxidation is only superficial. 
It is due to the formation of a hydrocarbonate of zinc, which 
covers the metal with an impermeable surface and protects it 
from further oxidation. 

When heated to redness in contact with the air, zinc vola- 
tilizes and burns with a greenish flame, being converted into 
oxide, which rises as smoke and fails in very light, white flakes, 
formerly called flowers of zinc or philosopher's wool. 

Zinc dissolves with evolution of hydrogen in hydrochloric 
and sulphuric acids, and in boiling solutions of potassium and 
sodium hydrates. When perfectly pure, it is dissolved with 
difiiculty by dilute sulphuric acid at ordinary temperatures, and 
the easy solubility of the metal of commerce must be attrib- 
uted to the presence of small quantities of foreign metals. The 
latter being electro-negative in contact with zinc, form voltaic 
couples, in which the zinc is the more oxidizable metal. 

Galvanized iron is iron covered with a thin layer of zinc ; it 
is prepared by plunging carefully- cleaned iron objects into a 
bath of molten zinc. 

Brass is an alloy of copper and zinc, obtained by melting the 
two metals together in crucibles. 

ZINC OXIDE. 

ZnO 

This oxide is prepared in the arts by heating zinc in large 
mufiles ; the product is separated from traces of metallic zinc 
by suspending it in water and rapidly decanting the white 
liquid. The zinc sinks to the bottom of the vessel before the 
lighter white powder has time to deposit ; the latter is therefore 
carried by the water into a second vessel, where it is allowed 
to settle. The process is called elutriation. 

Oxide of zinc is white ; it is irreducible by heat and is insolu- 
ble in water. A hydrate of this oxide is precipitated when an 
alkali is added to the solution of a zinc salt. 

ZnSO* + 2K0H = K^SO* -|- ZnfOH)^ 

Zinc sulphate. Zinc hydrate. 



ZINC SULPHIDE — ZINC CHLORIDE. 333 

An excess of alkali will redissolve the precipitate. 
Zinc oxide is largely used in the arts as a substitute for 
white lead as a pigment. 

ZINC SULPHIDE. 

ZnS 

The blende which occurs in nature is sulphide of zinc. It 
crystallizes generally in regular octahedra, sometimes in double 
pyramids of six faces (Friedel). 

On adding an alkaline sulphide to a neutral solution of a 
zinc salt a white precipitate is obtained, which is hydrated zinc 
sulphide. 

When moderately heated in contact with the air, zinc sul- 
phide absorbs four atoms of oxygen and is converted into sul^ 
phate. At a very high temperature it is converted into oxide, 
with formation of sulphurous oxide. 

ZINC CHLORIDE. 

ZnC12 

Zinc reduced to thin sheets will burn in chlorine. Zinc 
chloride is prepared in the laboratory by dissolving zinc in 
hydrochloric acid. The aqueous solution, evaporated to a 
syrupy consistence, deposits a hydrated chloride, ZnCP -f H'^O, 
crystallizing in deliquescent octahedra. This salt loses its 
water when strongly heated, and melts at about 250°. On 
cooling, a solid white mass is obtained, which is the anhydrous 
chloride ; in this state it is very avid of water and deliquesces 
when exposed to the air. It volatilizes without decomposition 
at a red heat. It is very soluble in water, and dissolves also 
in alcohol. 

ZINC SULPHATE. 

ZnSO* + 7H20 

This salt was formerly known as white vitriol. It is ob- 
tained by moderately roasting blende. The latter being often 
mixed with pyrites, zinc sulphate and ferrous sulphate are 
formed, and when the product of the roasting is lixiviated a 
solution of the two salts is obtained. The solution is evapo- 



334 ELEMENTS OP MODERN CHEMISTRY. 

rated, and the dry residue moderately calcined. The ferrous 
sulphate decomposes, yielding sulphuric acid, which distils, and 
ferric oxide, which remains mixed with the zinc sulphate. The 
residue being exhausted with water, the zinc sulphate dissolves 
and is deposited in crystals on the cooling of the concentrated 
solution. 

The salt may be prepared in the laboratory by ^dissolving 
zinc in dilute sulphuric acid : it is the residue in the prepara- 
tion of hydrogen. 

Sulphate of zinc crystallizes with 7 molecules of water. In 
this state it occurs as right rhombic prisms, isomorphous with 
magnesium sulphate. 

When heated, it melts in its water of crystallization, of 
which it loses 6 molecules ; the seventh it abandons only at 
238°. 

At a high red heat it is decomposed into zinc oxide, sul- 
phurous oxide, and oxygen. 

Zinc sulphate is very soluble in water, of which 100 parts 
dissolve 48.36 parts of the anhydrous salt at 10°, and 95.6 
parts at 100°. The solution has a styptic taste. 

Zinc sulphate forms crystallizable double salts with the alka- 
line sulphates ; thus, there is a double sulphate of zinc and 
potassium, containing 

ZnSO^.K^SO* + 6H^0 

Characters of Zinc Salts. — The zinc salts are colorless 
unless the corresponding acid be colored. Their neutral solu- 
tions are partially decomposed by hydrogen sulphide, which 
precipitates white sulphide of zinc ; the addition of a mineral 
acid prevents the precipitation ; the zinc salts of organic acids, 
such as the acetate and lactate, are completely decomposed by 
hydrogen sulphide. 

Ammonium sulphide produces a white precipitate of sul- 
phide; this reaction is characteristic. 

Potassium and sodium hydrates, and also ammonia, form 
white precipitates, soluble in an excess of the reagent. 

Potassium ferrocyanide gives a white precipitate. 



GALLIUM. 335 

GALLIUM. 

Ga = 69.9 

This metal was discovered in 1876 by Lecoq de Boisbaudran. 
It is contained in small quantity in certain blendes. One of 
the richest, found in Westphalia, contains only one sixty-thou- 
sandth of its weight. 

In order to extract the gallium, the ore is roasted, and the 
product dissolved in sulphuric acid. An acid liquor is thus 
obtained, containing principally sulphate of zinc, with sulphates 
of iron, aluminium, indium, etc., and a trace of gallium sul- 
phate. 

The following reactions are employed by Lecoq de Bois- 
baudran and Jungfleisch for the separation of the gallium : 

1. When the liquid is neutralized, the ferric oxide, alumina, 
and gallium oxide, which is a sesquioxide, are precipitated. 
The precipitate is redissolved in sulphuric acid, and the same 
operation repeated after converting the ferric oxide into ferrous 
oxide, which remains dissolved in the neutral liquid. By this 
means the greater part of the iron is removed. 

2. Grallium oxide dissolves, like alumina and zinc oxide, in 
an excess of potassium hydrate ; when this solution is saturated 
with hydrogen sulphide, the zinc is precipitated as sulphide, 
while the gallium and aluminium remain in solution. The 
greater part of the zinc is thus separated. 

3. When water is added to a boiling solution of gallium 
sulphate, the latter is precipitated as subsulphate, while alumi- 
nium sulphate remains in solution. 

4. Gallium oxide dissolves in an excess of ammonia ; alumina 
does not. 

5. Gallium separates in the metallic state when a voltaic 
current is passed through an alkaline solution of gallium oxide. 

Physical Properties. — Gallium has a metallic lustre recalling 
that of nickel. It readily crystallizes in forms derived from a 
right rhombic octahedron, generally in magnificent laminae. Its 
density is 5.96. It melts at 29.5°, and has a tendency to re- 
main in a state of superfusion. It is not volatile. 

This collection of properties gives to gallium a special place 
among the metals. It is one of the most remarkable of recent 
discoveries. 

Chemical Properties. — These are but little known at present. 



336 ELEMENTS OF MODERN CHEMISTRY. 

Gallium is oxidized but little, if at all, when heated in the air 
or in oxygen. It forms a sesquioxide, Ga'^O^ which resembles 
alumina in that it forms alums. Gallium alum was obtained 
by Lecoq de Boisbaudran. 

Gallium combines directly with chlorine, forming a solid, 
crystalline, and very volatile chloride. 



INDIUM. 

In = 113.4 

This metal was discovered in 1863 by Eeich and Richter 
in the zinc blendes of Freiberg (Saxony). It appears to exist 
in the majority of zinc blendes, and accompanies the zinc which 
is extracted from those minerals. It is ordinarily obtained 
from metallic zinc, which, however, contains only very small 
quantities of it. Commercial zinc (that of Freiberg is prefer- 
able) is digested in a quantity of dilute sulphuric acid insuffi- 
cient to dissolve all of the metal ; after several weeks, a spongy 
mass remains, which contains an excess of zinc and, indepen- 
dently of other metals, a small quantity of indium. This is 
the residue from which indium is obtained by processes which 
need not be here described. 

Indium is a brilliant metal, possessing almost the lustre of 
silver. It is soft and ductile. It melts at 176°, and is vola- 
tile, but less so than zinc and cadmium. It approaches these 
metals in its general chemical properties, but is more electro- 
negative, both of the latter metals precipitating it from its 
solutions. 

Indium is characterized by several spectroscopic lines, among 
which are a very brilliant blue and a less marked violet line. 
Winkler has indicated two other less distinct blue lines. 

Two oxides of indium have been described, a sesquioxide, 
In^O^, and a suboxide. The first is obtained by calcining the 
nitrate; it is yellow. When heated to 300° in a current of 
hydrogen, it is partially reduced, yielding a black suboxide. 

Indium cJdoride, In""CP, is formed when indium is heated 
in a current of chlorine. It is a snow-white, volatile solid. 



CADMIUJl. 337 

CADMIUM. 

Cd:=112 

Natural State and Extraction. — Cadmium is generally 
found associated with zinc, either as oxide in calamine, or as 
sulphide in zinc blende. As it is more volatile than zinc, it 
becomes concentrated in the first products of distillation. 

It is found especially, in the state of oxide, in the brown 
powder called cadmies, which condenses during the first hours 
of the distillation in the sheet-iron receivers adapted to the re- 
torts (Fig. 105). When mixed with powdered charcoal and 
calcined, this powder yields an alloy of zinc and cadmium 
which distils. 

The cadmium is extracted by dissolving the alloy in dilute 
sulphuric acid and passing a current of hydrogen sulphide 
through the acid liquid. The cadmium is precipitated as a 
yellow sulphide. This sulphide is dissolved in hydrochloric 
acid and the solution of cadmium chloride precipitated by am- 
monium carbonate. The cadmium carbonate thus obtained is 
calcined, and so converted into oxide, which is mixed with 
one-tenth its weight of powdered charcoal and heated in a clay 
retort. The cadmium distils. 

Properties. — Pure cadmium has a white lustre, but soon 
tarnishes in the air. Its density is 8.G0-8.69. It melts at 
320° (Person), and boils at 860° (H. Deville and Troost). It 
may be obtained crystallized in octahedra. 

It dissolves in dilute sulphuric and hydrochloric acids with 
evolution of hydrogen. 

Cadmium Oxide, CdO. — The oxide of cadmium may be ob- 
tained by calcining either the carbonate or nitrate. It has a 
yellowish-brown color, or a brown more or less deep. It is re- 
duced at high temperatures by carbon and by hydrogen, its 
reduction taking place more readily than that of zinc oxide. 

Cadmium Sulphide, CdS. — This sulphide occurs in nature 
in the form of bright yellow, hexagonal prisms, terminated by 
six-sided pyramids. 

It may be prepared in the laboratory by precipitating a solu- 
tion of a cadmium salt by hydrogen sulphide or a soluble sul- 
phide. An amorphous prcc-ipitatc of a fine yellow color is thus 
obtained. In this form it is employed in oil painting. 

Cadmium Iodide, CdP. — This salt is prepared by digesting 
P 29 



338 ELEMENTS OF MODERN CHEMISTRY. 

finely-divided cadmium with iodine in presence of water. It 
crystallizes from its aqueous solution in transparent and color- 
less, hexagonal prisms having a brilliant lustre. It is soluble 
in water and alcohol. 

Cadmium Sulphate, CdSO* + 4H'0.— Cadmium sulphate 
is obtained by dissolving the metal, or its oxide or carbonate, in 
dilute sulphuric acid. The neutral and concentrated solution 
deposits the salt in beautiful, right rectangular prisms. These 
crystals are efflorescent. 



COBALT. 

Co = 59 

Cobalt was discovered by Brandt in 1753. It is found prin- 
cipally in the state of arsenide, CoAs'^, and as sulph-arsenide, 
CoAsS (gray cobalt). Its ores are worked principally for the 
production of a dark-blue, vitreous mass, a combination of 
cobalt silicate and potassium silicate, known as smalt or azure 
blue. 

The metal is prepared in the laboratory by calcining its oxa- 
late in a covered crucible. 

CoC^O* = Co -h 2C0^ 

Cobalt oxalate. Carbon dioxide. 

It may be obtained as a metallic button by heating the pul- 
verulent metal in a lime crucible in a wind-furnace. The lime 
crucible is placed in another crucible of refractory clay, and 
the space between the two is filled up with fragments of quick- 
lime (H. Sainte-Claire Deville). 

Pure cobalt is silvery-white. It is very malleable ; its den- 
sity is 8.6, and it is magnetic. At ordinary temperatures it is 
unaffected by the air, but at a red heat it is converted into 
oxide. 

Oxides of Cobalt. — A monoxide, CoO, and a sesquioxide, 
Co'^O^, are known, and several intermediate oxides. 

The monoxide maybe obtained by calcining cobalt carbonate 
in close vessels. It is a greenish-gray or olive-green powder, 
which is reduced by hydrogen, charcoal, and carbon monoxide 
at a red heat. 

AVhen heated with borax before the blow-pipe, it dissolves, 
forming a blue glass. It is used for giving a blue color to 
glass and porcelain. 



COBALT. 339 

When an excess of potassium hydrate is added to the solu- 
tion of a salt of cobalt, a rose-red precipitate of cobalt hydrate, 
Co(OH)^ is formed. 

Cobalt sesquioxide, Co^O'^, is prepared by passing a current 
of chlorine through water, holding in suspension the rose- 
colored hydrate above mentioned. 

2CoO + H^O -f- CP = WO' + 2HCI 

The sesquioxide is deposited as a black powder, which may 
be dried by carefully heating it. 

Cobalt Chloride, CoCP. — When pulverulent cobalt is heated 
in a current of chlorine, it takes fire and is converted into a 
chloride, which sublimes in blue scales. A solution of this 
chloride may be obtained by dissolving either monoxide or car- 
bonate of cobalt in hydrochloric acid. The neutral solution is 
currant-red, and on evaporation deposits hydrated crystals of 
the same color. But when it is concentrated, after having 
added hydrochloric or sulphuric acid, it becomes blue. This 
change of color, due to the formation of anhydrous chloride 
even in the midst of the hot liquid, has caused the employ- 
ment of cobalt chloride as a sympathetic ink. Characters 
traced with the dilute solution, which is rose-colored, are invisi- 
ble on white paper, and appear blue only when the paper is 
warmed, again becoming invisible on cooling, by the absorption 
of atmospheric moisture. 

Cobalt Sulphate, CoSO* + 'ZH'O.— This salt is found in 
nature, crystallized in oblique rhombic prisms. It may be ob- 
tained by dissolving the oxide or carbonate in dilute sulphuric 
acid and concentrating the red solution. At ordinary temper- 
atures, the latter deposits red crystals, isomorphous with ferrous 
sulphate. Between 20 and 30°, it yields right rhombic prisms, 
containing 6 molecules of water, and isomorphous with magne- 
sium sulphate. 

Characters of Cobalt Salts. — The cobaltous salts are the 
more important. Their solutions are rose or currant-red, but 
when concentrated and hot they become blue, especially when 
an excess of acid is present. Hydrogen sulphide does not pre- 
cipitate solutions of cobalt salts. Ammonium sulphide forms 
a black precipitate. Potassium hydrate gives a blue precipitate 
of a basic salt, which, in presence of an excess of potassa, is 
converted into hydrate of cobalt, having a dirty rose color. 



340 ELEMENTS OF MODERN CHEMISTRY. 

Ammonia forms a blue precipitate, soluble in an excess of 
the reagent. 

When heated with borax in the blow-pipe flame, the salts of 
cobalt yield beads of a pure blue color. 



NICKEL. 

This metal was discovered by Cronstedt in 1751. 

Natural State and Extraction. — Nickel is found as arsen- 
ide, NiAs'^, in hupfernichel or nickeline. In the preparation of 
smalt from the ores of cobalt, which always contain nickel, the 
latter metal combines with the arsenic and a certain proportion 
of sulphur, forming a metallic-looking mass known as speiss. 

In the arts, nickel is extracted from kupfernickel or from 
speiss. In the laboratory it is prepared by reducing the oxide 
in a brasqued crucible, or by calcining the oxalate out of con- 
tact with the air. When heated to whiteness in a lime cruci- 
ble the nickel melts to a metallic button. 

Properties. — Pure nickel is grayish-white. It is malleable, 
ductile, and very tenacious. Its density is 8.279, and may be 
increased to 8.666 by hammering. Next to manganese, it is 
the hardest of the metals. It is less fusible than iron and more 
fusible than manganese. It is magnetic at ordinary tempera- 
tures, but loses this property at about 250°. It is unaltered by 
the air at ordinary temperatures, but absorbs oxygen at a red 
heat. It dissolves slowly in dilute sulphuric and hydrochloric 
acids, rapidly in nitric acid. In contact with concentrated nitric 
acid it becomes passive like iron. 

Nickel is used in the arts, in the manufacture of an alloy 
known as German silver, which contains 50 per cent, of copper, 
25 of nickel, and 25 of zinc. 

Nickel may be deposited as a brilliant metallic layer by the 
electrolysis of a solution of nickel and ammonium double sul- 
phate (A. C. and E. Becquerel). Adams made an application 
of this property to the nickel-plating of various objects by 
electro-metallurgy, and the process is now largely employed. 

Oxides of Nickel. — A monoxide, NiO, and a sesquioxide, 
Ni'^0^, are known. 

The anhydrous inonoxide is an ash-gray powder. It is 
obtained by strongly calcining the nitrate or carbonate. On 



NICKEL. " 341 

adding potassium hydrate to a nickel salt, an apple-green pre- 
cipitate of nickel hydrate, Ni(OH)^, is formed. 

Nickel sesquioxide may be obtained by moderately calcining 
the nitrate. It is black. When chlorine gas is passed into 
water holding nickel hydrate in suspension, a dark-brown pow- 
der is obtained, which is a hydrate of the sesquioxide. This 
hydrate may also be made by precipitating a nickel salt with 
potassium hydrate mixed with an alkaline hypochlorite. 

When strongly calcined, nickel sesquioxide abandons part of 
its oxygen and is changed into monoxide. Treated with hydro- 
chloric acid, it yields nickel chloride, and chlorine is disengaged. 

Ni^O^ 4- 6HC1 = 2NiCP + 3H^0 -f CP 

Nickel Chloride, NiCP. — This salt may be obtained anhy- 
drous by the action of chlorine on nickel-filings ; it is volatile 
at a dull-red heat, and sublimes in golden-yellow scales. The 
hydrated chloride is formed by the action of boiling water on 
the anhydrous salt, or by the action of hydrochloric acid on the 
oxide or carbonate. Its solution is green, and after proper 
concentration deposits beautiful green crystals which contain 
NiCP + QH^O. 

Nickel Sulphate, NiSO* + YH^O.— The sulphate is depos- 
ited in fine, emerald-green, orthorhombic prisms, isomorphous 
with magnesium sulphate, when its solution is allowed to evap- 
orate spontaneously below 15°. There is another hydrate con- 
taining 6H'^0, which is dimorphous. When deposited between 
20 and 30°, it crystallizes in square octahedra, but when its 
solution is made to crystallize between 60 and 70°, right rhom- 
bic prisms are obtained, isomorphous with the corresponding 
sulphates of magnesium, zinc, and cobalt. 

Nickel sulphate dissolves in 3 times its weight of water at 10°. 

Characters of Nickel Salts. — The nickel salts when hy- 
drated or in solution have a fine emerald-green color. When 
anhydrous they are yellow. 

Hydrogen sulphide does not precipitate them from acid solu- 
tions. Ammonium sulphide throws down a black precipitate. 
Potassium hydrate and potassium carbonate form apple-green 
precipitates. 

In neutral solutions, ammonia gives a green precipitate of 
nickel hydrate, which dissolves in an excess of ammonia, form- 
ing a blue solution. 

29* 



342 ELEMENTS OF MODERN CHEMISTRY. 

MANGANESE. 

Mil = 55 

This metal has been obtained as a coherent, very hard mass, 
by reduction of either manganous carbonate or red oxide of 
manganese with charcoal or sugar in a lime crucible at the 
highest heat of a wind-furnace (H. Deville). 

It is whitish-gray, and almost as infusible as platinum. Its 
density is 7.2. Its powder decomposes warm water. 

MANGANESE OXIDES. 

Manganese forms six compounds with oxygen : 

Manganous oxide MnO 

Manganoso-manganic oxide Mn^O* 

Manganic oxide Mn^O^ 

Manganese dioxide MnO^ 

Manganic anhydride MnO^ 

Permanganic anhydride Mn^QT 

Manganous oxide is formed when manganous carbonate is 
strongly heated in a current of hydrogen. Carbon dioxide is 
evolved, and a green powder, which is manganous oxide, re- 
mains. It takes fire on contact with an incandescent body, and 
is converted into a brownish-red powder, which is red oxide of 
manga,nese. 

3MnO + = Mn^O* 

The latter body is also formed by the calcination of the diox- 
ide. It is analogous to the magnetic oxide of iron, and con- 
stitutes the mineral known as haiismannite. 

Manganic oxide^ Mn^O^, occurs in nature in the crystallized 
state as hraunite. It is isomorphous with alumina and ferric 
oxide. 

MANGANESE DIOXIDE. 

(bINOXIDE or PEROXIDE OF MANGANESE.) 
Mn02 

This important body is found abundantly in nature ; it con- 
stitutes the mineral pyrolusite. It may be obtained pure and 
anhydrous by exposing a concentrated solution of manganous 
nitrate to heat and gradually raising the temperature to 155°. 



MANGANIC ACID. 343 

Nitrous vapors are evolved, and a brilliant brown-black mass is 
obtained, which is the dioxide. 

Mn(NO^0' = MnO^ + 2N0' 
It loses one-third of its oxygen when heated to redness, and 
is converted into the red oxide. When heated with concen- 
trated sulphuric acid, it loses half of its oxygen, manganous 
sulphate being formed, 

MnO^ + H^SO* = MnSO* + H^O + 

With hydrochloric acid it yields water, chlorine, and manga- 
nous chloride. 

A hydrate of manganese dioxide is formed when an excess 
of chlorine is directed into water holding in suspension man- 
ganous hydrate or carbonate. This hydrate is a dark-brown 
powder. 

Manganese dioxide is largely employed for the preparation 
of oxygen and chlorine. It is used to decolorize glass black- 
ened by carbonaceous matters or rendered green by a trace of 
iron. 

MANOANIC ACID. 

When manganese dioxide is heated with potassium hydrate 
in a silver crucible, and the calcined mass is exhausted with 
water, the latter dissolves out potassium manganate. A dark- 
green liquor is thus obtained which, when evaporated in vacuo, 
deposits a crystalline mass. These crystals may be drained on 
a porous porcelain plate, and green needles of potassium man- 
ganate, K'^MnO^ remain. The salt is isomorphous with the 
sulphate K^SO*. 

When the green solution is boiled, it becomes red and deposits 
brown flakes of hydrated manganese dioxide : the red liquor is 
a solution of potassium permanganate, this salt being formed at 
the expense of the manganate, which breaks up into hydrated 
dioxide, potassium hydrate, and permanganate. 

3K^MnO* + 3H20 = K^Mn^O« + MnO^H^O + 4K0H 

Potassium Potassium Hydrated mauganese 

manganate. permanganate. dioxide. 

An analogous decomposition takes place when an acid is 
added to the green solution of manganate ; a manganous salt 
and permanganic acid are formed, and the latter colors the 
liquid red. 



344 ELEMENTS OF MODERN CHEMISTRY. 



PEEMANaANIC ACID. 

Potassium permanganate, K^Mn'^0^, is an important salt. It 
may be prepared by introducing into an iron crucible 5 parts 
of caustic potassa with a small quantity of water, then a mix- 
ture of 3 J parts of potassium chlorate and 4 parts of finely- 
powdered manganese dioxide. The mixture is heated and 
continually stirred, until the mass becomes dry and the tem- 
perature has reached dull redness. After cooling, the product 
is pulverized and introduced into 200 parts of boiling water. 
When the liquid has assumed a purple color, it is allowed to 
stand, decanted, and after neutralization by nitric acid, is 
evaporated at a gentle heat. On cooling, it deposits crystals 
that may be dried on a porous tile. 

Potassium permanganate crystallizes in almost black needles, 
having a metallic reflection. It dissolves in 15 or 16 parts of 
cold water, and its solution has a magnificent, intense purple 
color. 

If solution of sulphurous acid be added to potassium per- 
manganate solution, the latter is instantly decolorized, and the 
liquid contains only potassium sulphate and manganese sulphate. 

If a drop of the solution of potassium permanganate be 
placed upon a sheet of paper, it loses its color and a brown 
stain of hydrated manganese dioxide is produced. 

These experiments indicate the oxidizing properties of the 
permanganate. In the first, sulphurous acid was oxidized ; in 
the second, it was paper, of which the carbon and hydrogen 
removed the oxygen from the permanganate, which was thus 
reduced to dioxide. 



MANGANOUS SULPHATE. 

MnSO* + 7H20 

This salt may be prepared by dissolving manganous carbon- 
ate in sulphuric acid. The properly concentrated rose-colored 
solution deposits, between and 6°, oblique rhombic prisms, 
isomorphous with green vitriol and containing 7 molecules of 
water. 

Between T and 20°, manganous sulphate crystallizes with 5 



MANGANOUS CARBONATE. 345 

molecules of water, like cupric sulphate, with which it is then 
isomorphous. 

Between 20 and 30°, it is deposited in oblique rhombic 
prisms, according to Marignac, which contain only 4 molecules 
of water. 

All of these crystals are rose-colored, and their color is 
deeper as they contain more water of crystallization. They are 
very soluble in water. 



MANGANOUS CARBONATE. 
MnC03 

The residues from the preparation of chlorine may be used 
for making this salt. They are evaporated, without filtering, 
in a porcelain capsule, with frequent stirring, and the dry 
residue is calcined with an excess of manganese dioxide. The 
ferric chloride which was mixed with the manganous chloride 
is decomposed or volatilized during this operation. Ferric 
oxide remains, mixed with the excess of manganese dioxide 
and the manganous chloride, which resists the heat. The latter 
is extracted by exhausting the mass with boiling water. A 
rose-colored solution is thus obtained which often contains a 
small quantity of cobalt chloride. The latter is precipitated 
as sulphide by adding little by little a solution of sodium sul- 
phide. As soon as the precipitate, which is at first blackish, 
begins to assume a flesh tint, the liquid is filtered and precipi- 
tated by sodium carbonate. 

Manganese carbonate constitutes a white powder with a pale 
rose tint. When heated in contact with air, it gives up car- 
bonic acid gas and is converted into red oxide of manganese. 

Characters of Manganese Salts. — The salts of manganese 
are colorless or have a light rose color. Their solutions are 
not precipitated by hydrogen sulphide. Ammonium sulphide 
gives a flesh-colored precipitate ; sodium carbonate, a dirty 
white. Potassium hydrate produces a dirty white precipitate 
of manganous hydrate, which rapidly becomes brown by ab- 
sorbing oxygen from the air. 

When heated in the blow-pipe flame with a small quantity 
of potassium hydrate or nitrate, the salts of manganese give a 
bead which dissolves in water with a green color (manganate). 
p* 



346 ELEMENTS OF MODERN CHEMISTRY. 



CHROMIUM. 

Cr ^ 52.5 

Chromium was discovered in 1797, by Vauquelin, in a min- 
eral formerly known as red lead of Siberia, and which is 
chromate of lead. It forms one of the elements of chrome 
iron, a combination of chromium oxide with ferrous oxide, 
Cr^O'^FeO, which corresponds to magnetic oxide of iron, 
Fe^OlFeO. 

H. Deville isolated the metal by calcining chromium oxide 
with charcoal and linseed oil in crucibles of lime and charcoal. 
Thus prepared, chromium forms grayish- white, metallic grains, 
which are brittle, as hard as corundum, and have a density of 
5.9. 

This metal does not oxidize in the air at ordinary tempera- 
tures. At a red heat, it is converted into the oxide Cr'^0^. 
When thrown into potassium chlorate in a state of fusion, it 
burns with a dazzling white flame, a chromate being formed. 
It burns in the same manner in chlorine gas, being transformed 
into a violet chloride. It dissolves in hydrochloric acid, disen- 
gaging hydrogen. 

COMPOUNDS OF CHROMIUM AND OXYGEN. 

There are two well-defined compounds of chromium and 
oxygen, the green oxide of chromium, Cr'^0^ and chromic 
anhydride, CrO^. 

Chromium Oxide, Cr^O^, is a green powder; it may be 
obtained by calcining mercurous chromate. 

2Hg^CrO* = 4Hg + 0^ + Cr'^0^ 

Another process consists in heating in a crucible a mixture 
of 2 parts of potassium dichromate with a little more than 1 
part of flowers of sulphur. After cooling, the mass is treated 
with water, which dissolves out potassium sulphate and leaves 
chromium oxide. 

Fremy obtained it in small crystals by passing chlorine gas 
over potassium chromate heated to redness, and exhausting the 
cooled mass with water. 

Chromium oxide is undecomposable by heat, and melts only 
at the temperature of the forge. It forms several different 



CHROMIC ANHYDRIDE — CHROMATES. 347 

hydrates. When ammonia is added to the green solution of 
chromic chloride, a green, flaky precipitate of chromic hydrate 
is formed; it is soluble in acids and in potassium hydrate. 

Chromic Anhydride, CrO^ is prepared by gradually adding 
to a cold saturated solution of potassium dichromate 1? times 
its volume of sulphuric acid. The chromic anhydride, ordina- 
rily called chromic acid, set free separates in needle-shaped 
crystals of a dark-red color, which should be drained and re- 
crystallized in a small quantity of warm water. 

It is deliquescent; its aqueous solution has a dark yellow- 
brown color. It is an energetic oxidizing agent. Hydrochlo- 
ric acid converts it into chromic chloride, with evolution of 
chlorine. 

2CrO=^ -f 12HC1 = Cr^CP + GH^O -f 3CP 

If a concentrated solution of sulphurous acid be added to a 
solution of chromic acid, the liquid immediately becomes green 
from the formation of chromic sulphate. 

Chromates. — The most important chromates are those of 
potassium and lead. 

Potassium neutral chromate, K^CrO*, crystallizes in lemon- 
yellow, right rhombic prisms, isomorphpus with potassium sul- 
phate. It is very soluble in water, to which it communicates 
an intense yellow color. So great is its coloring property, that 
one part of chromate will sensibly color 40,000 parts of water. 

Potassium dichromate, K"''Cr'^0^ is prepared by heating to 
redness 2 parts of chrome iron with 1 part of nitre. The mass 
is exhausted with water, which dissolves out potassium neutral 
chromate; acetic acid is added to this solution, precipitating 
the silica, which is derived from the crucible and remains in 
the solution as silicate, and removing one-half of the potassium 
from the chromate, thus converting it into the dichromate. 
The latter crystallizes out on evaporation. 

Potassium dichromate is a beautiful salt of an orange-red 
color. It crystallizes in quadrangular tables derived from a 
dissymetric prism. 

It dissolves in 8 or 10 parts of cold water and in a much 
less quantity of boiling water. 

A strong heat decomposes it into neutral chromate, chromium 
oxide and oxygen. 

2K^Cr^0^ =. 2K^CrO* + Cr^O=^ + 0^ 



348 ELEMENTS OF MODERN CHEMISTRY. 

When heated with sulphuric acid, it loses oxygen and is 
converted into chromic sulphate and potassium sulphate. 

K'-^Cr'^O^ + 4H^S0* = CrXSO^^ + K'^SO* -f- 4ffO -f 0^ 

The residue when exhausted with water yields a green solu- 
tion, which deposits on evaporation beautiful octahedral crystals 
of a violet-black color, constituting chrome alum. 

Cr\SO*/.K^SO^ + 24H^O 

Sulphurous acid reduces potassium dichromate in the cold, 
also yielding chrome alum if sulphuric acid be added. 

K^Cr^O^ H- BSO'^ + H^SO* = Cr\SO*)lK'^SO* + H^O 

The constitution of potassium dichromate is represented by 
the formula 

KOCrO^ 

> 

KOCrO^ 



COMPOUNDS OF CHROMIUM AND CHLORINE. 

Several combinations of chromium and chlorine are known. 
The most important is the violet chloride, Cr^CP, correspond- 
ing to aluminium chloride and ferric chloride. It is prepared 
by passing chlorine gas over an intimate and perfectly dry 
mixture of chromium oxide and charcoal, heated to redness in 
a porcelain tube ; carbon monoxide is disengaged, and chromic 
chloride sublimes into the cooler portion of the tube in brilliant 
peach-blossom-colored scales. 

These crystals are almost insoluble in cold water, and dis- 
solve but slowly in boiling water. Hydrogen reduces them at a 
red heat, with formation of hydrochloric acid, and a chloride, 
Cr^Cl*, which crystallizes in white scales (Peligot). 

Cr'^CP + H'^ = 2HC1 + Cr^Cl* 

If a small quantity of the chloride Cr^Cl*, be added to hot 
water, holding in suspension the violet chloride, CrCP, the 
latter will be instantly dissolved, forming a green solution. 

Chlorochromic anhydride^ CrO'CP, is obtained by heating a 
previously fused mixture of common salt and potassium di- 
chromate with sulphuric acid ; abundant red vapors are disen- 



BISMUTH. 349 

gaged, and condense to a blood-red liquid. This body boils 
at 116.8^. Its density at 25° is 1.920 (Thorpe). On contact 
with water it decomposes into hydrochloric acid and chromic 
anhydride. 

CrO^Cl^ + IPO = CrO^ + 2HC1 



BISMUTH. 

Bi = 210 

Extraction. — This metal is found native in a quartzy gangue. 
It is extracted by simply heating the mineral in cast or sheet 
iron tubes, which are arranged in an inclined position in a fur- 
nace. The bismuth melts and runs out at an opening in the 
lower end of the tubes. 

The bismuth of commerce is never pure ; it contains traces 
of other metals, nearly always of arsenic and sometimes of 
sulphur. It is purified by pulverizing it, mixing it with 2V 
its weight of potassium nitrate, and heating the mixture to 
redness in a clay crucible. The foreign metals more oxidiza- 
ble than the bismuth are thus converted into oxides, the ar- 
senic into arsenate of potassium, and the sulphur into potassium 
sulphate. This treatment may be repeated a second time if 
necessary. 

Properties. — Bismuth is a whitish-gray metal, having a yel- 
low lustre. Its fracture is crystalline and laminated. Its den- 
sity is 9.83, and it melts at 264°. On cooling, it crystallizes 
in rhombohedra, of which the surfaces become covered with a 
thin film of oxide, causing a beautiful iridescent play of colors 
like that on a soap-bubble. 

Bismuth increases in volume on solidifying. It volatilizes at 
a white heat. It is unaltered by the air at ordinary tempera- 
tures, but at a red heat it absorbs oxygen and burns, forming 
bismuth oxide. Its best solvent is nitric acid, which converts 
it into nitrate. 

The various compounds of bismuth present great analogy to 
those of antimony, next to which this metal might be placed 
in the group including nitrogen, phosphorus, arsenic, antimony, 
and bismuth. 

30 



350 ELEMENTS OP MODERN CHEMISTRY. 

This analogy is shown in the following synoptic table : 
BiCP SbCP 

Bismuth trichloride. Antimony trichloride. 

Bismuth trioxide. Antimony trioxide. 

Bi^O^ Sb^O^ 

Bismuthic anhydride. Antimonic anhydride. 

Bi^O* Sb^O* 

Bismuth Lismuthate. Antimony antimonate. 

Bi^S=^ Sb^S^ 

Bismuth trisulphide. Antimony trisulphide. 

Otherwise, bismuth is related to the metals proper, not only 
by its properties, but by the facility with which it forms defi- 
nite salts. It is triatomic in its more important combinations, 
the oxide, chloride, and nitrate. 



BISMUTH TRIOXIDE. 

BI203 

This body is obtained by decomposing the nitrate by heat. 
It is a straw-yellow powder, fusible at a red heat, and yielding 
on cooling a dark-yellow, vitreous mass. It attacks clay cruci- 
bles even more rapidly than litharge. 

A hydrated oxide of bismuth is formed when the nitrate or 
subnitrate is treated with potassium hydrate or ammonia. It 
is a white powder, insoluble in an excess of alkali, and when 
boiled with potassa, is converted into the crystalline anhydrous 
oxide. 

BISMUTH TRICHLORIDE. 

BiCP 

Finely-divided bismuth will burn in chlorine, being con- 
verted into chloride. The latter is prepared by directing a 
current of chlorine upon melted bismuth contained in a retort. 
The chloride distils and solidifies in the receiver to a fusible, 
crystalline, and deliquescent mass, formerly known as butter 
of bismuth. A crystallized, hydrated chloride of bismuth may 
also be obtained by evaporating a solution of bismuth in nitro- 
hydrochloric acid. 

Bismuth chloride dissolves in water charged with hydro- 
chloric acid, but is decomposed when treated with pure water ; 



BISMUTH NITRATE. 351 

in the latter case an oxychloride is formed and precipitated as 
a fine, white powder, hydrochloric acid being at the same time 
formed. 

2BiCP -[- 211^0 = 2BiOCl -f 4HC1 

Bismuth oxychloride is known as pearl-wMte. It contains 
BiOCl. 

BISMUTH NITRATE. 

Bi(N03)3 

Bismuth dissolves readily in nitric acid, and the concentrated 
solution deposits large, four-sided prisms, which are colorless 
and deliquescent. They contain BiCNO^)' + 3H"^0. They 
are very soluble in water acidulated with nitric acid, but if this 
solution be poured into a large excess of water, a pulverulent, 
white precipitate is formed, and increases in volume if very 
dilute ammonia be gradually added to the liquid in order to 
partly neutralize the free acid. 

This precipitate is much employed in medicine under the 
name of subnitrate of bismuth. Its composition is generally 
expressed by the formula BiNO* + H^O = (BiOj'NO' + 
H^O. 

It may be regarded as bismuthyl nitrate, that is, nitric 
acid, HNO^, in which the monobasic atom of hydrogen is re- 
placed by the monatomic group BiO. Or it may be considered 
as a derivative of orthonitric acid, H^NO*, corresponding to 
orthophosphoric acid, H^PO* (page 191). 

Boiling water removes still more nitric acid from this sub- 
nitrate, leaving a residue, which is used as a cosmetic, known as 
hlanc de fard. 

Characters of Solutions of Bismuth. — When mixed with 
a large quantity of water, bismuth solutions give white pre- 
cipitates of sub-salts. Hydrogen sulphide, and the soluble 
sulphides form a brown precipitate of bismuth sulphide, insolu- 
ble in an excess of ammonium sulphide. The alkaline hydrates 
and carbonates give white precipitates, insoluble in an excess 
of the reagent. 

Bismuth solutions are not precipitated by either sulphuric 
or hydrochloric acid. 

When heated with sodium carbonate in the reducing flame of 
the blow-pipe, compounds of bismuth yield a metallic globule, 
very brittle after cooling. 



352 



ELEMENTS OF MODERN CHEMISTRY. 



Tiisr. 

Sii (Stannuin) = 118 

Natural State and Extraction. — The only mineral of tin 
which is worked is the dioxide (cassiterite). It is found in 
veins in the oldest formations, or disseminated in sand produced 
by their disaggregation. The principal tin mines are in India, 
in Malacca and the island of Banca, in Wales and in Saxony. 
Tin ore generally occurs mixed with various other minerals, 
such as sulphide and sulph-arsenide of iron, sulphides of copper 
and tin, etc. It is crushed and washed in order to remove 
light, earthy matters, and then roasted. The sulphides and 
sulph-arsenides are thus oxidized and disintegrated, and the 

product is submitted to a sec- 
ond washing which removes 
the lighter oxides, leaving the 
cassiterite. The latter is then 
heated with charcoal in a 
cupola-furnace, represented in 
Fig. 108; it is a sort of pris- 
matic furnace, having a hearth 
at the bottom where the melted 
metal collects. Air is blown 
in through the tuyere D. Car- 
bon monoxide is formed, and 
this reduces the stannic oxide ; 
the tin collects on the hearth, 
from which it is drawn into 
the basin I, where it is stirred 
with rods of green wood. The 
steam and gases produced by 
the carbonization of the wood, agitate the melted mass and bring 
to the surface the foreign matter or dross, which is removed. 
The tin is then run into moulds. 

Thus obtained, tin generally contains small quantities of 
copper, iron, lead, antimony, and arsenic. It is purified by 
slowly heating it on the hearth of a reverberatory furnace; 
the pure tin melts first and runs out of the furnace, while the 
less fusible alloys remain upon the hearth. This method of 
purification is called liquation. 

Properties. — Pure tin is a white metal, resembling silver in 




Fig. 108. 



TIN. 353 

its color and lustre. It melts at 228°, and crystallizes when 
slowly cooled. Crystals of tin, belonging to the type of the 
right square prism, may also be obtained by galvanic precipi- 
tation of the metal. Their density is 7.1*78. That of the 
fused and slowly-cooled metal is 7.373 (H. Deville). 

Tin is ductile and malleable. When a bar of tin is bent, 
it produces a peculiar noise called the cry of tin. 

The metal is unaltered by the air, but when fused, rapidly 
becomes covered with a grayish pellicle of oxide. Tin dis- 
solves in concentrated hydrochloric acid, disengaging hydrogen. 
The action is rapid when heat is applied. 

If ordinary nitric acid be poured upon granulated tin, an 
energetic action takes place immediately. The tin is converted 
into a white powder of dioxide, and torrents of red vapors are 
evolved. 

Very dilute nitric acid attacks tin almost without disengage- 
ment of gas. After some time the liquid. will be found to con- 
tain a small quantity of tin nitrate and ammonium nitrate. 
The ammonia is formed by the simultaneous reduction of water 
and nitric acid by the tin. 

HNO^ + WO = 20^ + Nff 

When tin is heated with a concentrated solution of either 
potassium or sodium hydrate, hydrogen is disengaged, and an 
alkaline stannate is formed. 

Uses of Tin. — Tin enters into the composition of bronzes; 
it is made into dishes and covers, and the thin foil in which 
various substances, such as chocolate and tobacco, are enveloped. 

Tinning of kitchen vessels consists in covering them with a 
thin coating of tin. This protects the copper or iron from the 
action of the acids which enter into the composition of various 
articles of food. The objects to be tinned are first well cleaned 
by rubbing them with sand, and are then dipped into melted 
tin. After separating the excess of metal, they are polished 
by rubbing with cloths dipped in sal ammoniac. 

Tin-plate is sheet-iron covered with a thin layer of tin. The 
iron is first dipped into dilute sulphuric acid to remove the 
oxide; it is then rubbed with sand, and afterwards plunged 
successively into a bath of melted tallow and a bath of tin covered 
with tallow. On contact with the iron, the tin enters into com- 
bination, forming a true alloy, which becomes covered with a 
coating of pure tin. 

30* 



354 ELEMENTS OF MODERN CHEMISTRY. 

When the surface of tin-plate is washed with a mixture of 
hydrochloric and nitric acids, the superficial coat of tin is dis- 
solved, and the crystallized alloy of tin and iron is exposed. 
This is called crystallized tin-plate. 

COMPOUNDS OF TIN AND OXYGEN. 

Tin forms two compounds with oxygen, stannous oxide, SnO, 
and stannic oxide, SnO'^ The first is of but little importance. 
It is obtained by precipitating a solution of stannous chloride 
by potassium hydrate, and boiling the precipitate, by Avhich the 
white, stannous hydrate first formed is converted into a black 
crystalline powder of stannous oxide. When this substance is 
heated to 250°, it decrepitates, increases in volume, and becomes 
converted into an olive-brown powder, which is a dimorphous 
modification of the black oxide. 

STANNIC OXIDE. 

Sn02 

This body is found in nature in the form of beautiful, hard, 
transparent crystals of a yellowish-brown color, belonging to 
the type of the square prism. 

The white powder obtained when the metal is treated with 
nitric acid is a stannic hydrate, which plays the part of an acid, 
and was named by Fremy metastannic acid. He attributes to 
it the composition 5(H*SnO*). It would be a polymere of 
normal stannic acid. 

|^,J0*-=(0HySn- 

When heated to 100°, this hydrate loses half of its water; 
at a red heat, it loses the remainder and is converted into stannic 
oxide. 

When ammonia is added to an aqueous solution of stannic 
chloride, a white, gelatinous precipitate is formed, constituting 
a hydrate. 

H^SnO^ = ^{^I I 0^ 

This is the stannic acid of Fremy. It dissolves readily in 
hydrochloric acid, and the solution behaves as would an aqueous 
solution of stannic chloride. 

H^SnO^' 4- 4HC1 == SnCl* + 3H^0 



SULPHIDES OF TIN — STANNOUS CHLORIDE. 355 

It reacts with tlie bases, forming stannates of whicli the 
general composition is expressed by the formula: 

K-^SnO^ = R^ j ^' 

When heated to 140°, or even when dried for a long time 
in a vacuum, it becomes insoluble in acids. 

SULPHIDES OF TIN. 

Two sulphides of tin are known : a monosulphide, SnS, and 
a disulphide, SnS^ The first is obtained by heating tin-filings 
with flowers of sulphur : the product still contains an excess 
of tin, and it is necessary to again heat it with a fresh quantity 
of sulphur. It is a crystalline, lead-colored mass. 

Tin disulphide or stannic sulphide is prepared by first making 
an amalgam of 12 parts of tin and 6 parts of mercury ; this is 
pulverized and the powder is mixed with 7 parts of flowers of 
sulphur and 6 parts of sal-ammoniac. The mixture is intro- 
duced into a matrass of green glass and gradually heated to 
dull redness on a sand-bath. Sulphur, sal-ammoniac, sulphide 
of mercury, and stannous sulphide are condensed in the upper 
part of the matrass, of which the interior becomes covered with 
a yellow crystalline mass of stannic sulphide. The presence 
of sal-ammoniac and mercury, which volatilize in this opera- 
tion, prevents an elevation of temperature, which would decom- 
pose the stannic sulphide. The latter is carried with their 
vapors, and condenses in brilliant, gold-like scales, which are 
greasy to the touch. This body is known as mosaic gold. It 
is decomposed by a red heat into stannous sulphide and sul- 
phur. It is used for coating the cushions of electric machines. 

STANNOUS CHLORIDE. 

SnCP 

This compound may be prepared anhydrous by heating tin 
in hydrochloric acid gas. Hydrogen is evolved, and a white 
or grayish mass remains, which has a greasy appearance, and 
is almost transparent. It .fuses at 250°. This is stannous 
chloride. 

When tin is dissolved in hot, concentrated hydrochloric acid 
and the limpid solution is evaporated and allowed to cool, 
beautiful transparent crystals are obtained, which contain 



356 ELEMENTS OF MODERN CHEMISTRY. 

SnCP -|- 2H^0. This is known in commerce as tin salt or tin 
crystals. 

The crystals of stannous chloride dissolve in a small quan- 
tity of water, forming a limpid liquid, but when treated with 
a large quantity of water, they yield a cloudy liquid, which 
holds in suspension a small quantity of white oxychloride. 
The atmospheric oxygen dissolved in the water takes part in 
this decomposition of stannous chloride, from which it removes 
part of the metal, a corresponding quantity of stannic chloride 
(tetrachloride) being formed. 

Stannous chloride reduces many oxygenized and chlorinated 
compounds. It decomposes the salts of silver and mercury, 
setting free the metal. It instantly decolorizes the purple 
solution of potassium permanganate. 

If a solution of stannous chloride be added to a solution of 
corrosive sublimate (mercuric chloride), a white precipitate of 
calomel (mercurous chloride) is instantly formed. By adding 
an excess of stannous chloride, all of the chlorine may be re- 
moved from the mercuric chloride, and a gray precipitate of 
metallic mercury will be formed. 

Stannous chloride is employed as a mordant in dyeing. 



STANNIC CHLORIDE (TETRACHLOEIDE OF TIN). 

SnCl* 

If thin tin-foil be thrown into a jar of chlorine gas, the 
metal will take fire, and in presence of an excess of chlorine 
will be converted into anhydrous stannic chloride. This is 
liquid, and gives off white fumes in the air. It was formerly 
known as fuining liquor of Lihavius. 

It is prepared by passing dry chlorine upon tin contained in 
a small retort. The anhydrous chloride condenses in the re- 
cipient in the form of a yellow liquid. It may be decolorized 
by rectification with a small quantity of mercury, which removes 
the excess of chlorine. 

Tin tetrachloride boils at 120°. Its density is 2.28. A 
small quantity of water added to it is absorbed with a hissing 
noise, and the formation of a crystalline deposit of a hydrate, 
SnCl* + 5H^0. 

These crystals may also be obtained by dissolving tin in aqua 
regia and evaporating the solution, or, again, by passing chlo- 



LEAD. 357 

rine into a solution of stannous chloride and concentrating the 
solution. 

The crystals of hydrated stannic chloride dissolve in water, 
forming a clear solution. 

Characters of Stannous Solutions. — Brown precipitates 
are formed by both hydrogen sulphide and ammonium sulphide ; 
the precipitate dissolves in an excess of the latter reagent. 

Potassium hydrate forms a white precipitate, soluble in an 
excess of potassa ; ammonia yields a white precipitate, insoluble 
in excess. 

An excess of stannous chloride produces a gray precipitate 
of metallic mercury in a solution of mercuric chloride. 

Chloride of gold gives a purple precipitate (purple of Cas- 
sius) in dilute stannous solutions. 

Characters of Stannic Solutions. — Hydrogen sulphide and 
ammonium sulphide form yellow precipitates, soluble in a large 
excess of the latter reagent. Potassa, soda, and ammonia, 
all form white precipitates, disappearing in an excess of the 
reagent. 

Chloride of gold does not precipitate stannic solutions. 

A sheet of iron or zinc will precipitate the tin from either 
stannous or stannic solutions in gray scales, which assume the 
metallic lustre when burnished. 



LEAD. 

Pb(Plumbum) = 207 

Treatment of Lead Ores. — The minerals of lead which are 
worked are the carbonate, and especially the sulphide, known as 
galena. 

The extraction of the metal from the carbonate is simple : 
it is heated with charcoal in a cupola-furnace, and the reduced 
lead collects on the hearth. 

Two methods are employed for the reduction of galena. 
One consists in melting the ore with iron (granulated cast iron). 
Sulphide of iron is formed, and both it and the reduced lead 
enter into fusion and separate from each other by virtue of 
their different densities, the lead being much the heavier. 
This is the reduction method. It is employed for impure ores 
having a silicious gangue. 

By the other process, known as the reaction method, the 



358 



ELEMENTS OF MODERN CHEMISTRY. 



galena is first roasted, by which the sulphide is partially trans- 
formed into oxide and sulphate ; the openings of the furnace 
are now closed and the temperature is elevated. The excess 
of sulphide then reacts upon the oxide and upon the sulphate ; 
sulphurous acid gas is disengaged, and metallic lead is formed. 
This is called work-lead. 

PbS + 2PbO == 3Pb + SO^ 
PbS + PbSO^ = 2Pb + 280^ 

The operation is conducted in a reverberatory furnace repre- 
sented in Fig. 109. The ore is spread in thin layers on the 




$$^^^M;j^^^^^\\^ 



.^^x^nNs^-^^^^^^^^V^ 



Pig. 109. 



hearth E, and heated to dull redness ; the fire is at A, and the 
air enters by the openings D. These are closed when it is 
judged by the aspect of the mass that the roasting is suffi- 
ciently advanced. The heat is then increased. 

Independently of the portion of lead sulphide which reacts 
upon the oxide and sulphate, there is always an excess, which 
melts when the heat is increased, and separates in the form of 
lead matt. This is subjected to another operation by the same 
process of reaction, and furnishes a harder lead than that first 
obtained ; it contains a small quantity of copper, and is known 
as slag lead. 

In some works, charcoal-powder is added at a certain stage 
of the roasting, to remove the oxygen from the oxide and sul- 
phate formed. 



LEAD. 



359 



Treatment of Argentiferous Lead. — The lead produced by 
these methods, and especially the work-lead, often contains a 
small proportion of silver. In order to separate the latter 
metal, the lead is submitted directly to cupellation, or is first 
refined by way of crystallization before the cupellation. 

The object of rejimng hy crystallization is the formation of 
an alloy of lead and silver, richer in silver than the work-lead. 
The argentiferous lead is melted and allowed to cool slowly; 
nearly pure lead separates in the form of crystals, which are 
deposited at the bottom of the molten metal. These are re- 
moved by a ladle as fast as they are formed ; the richer alloy 




Fig. 110. 

of lead and silver remains liquid. The crystals of lead still 
contain a little silver, and are submitted to another fusion ; lead 
again crystallizes out on cooling, and a small quantity of an 
alloy still rich in silver is obtained. The same operation re- 
peated a third time determines the separation of pure lead. 
The alloys of lead and silver thus obtained are themselves sub- 
mitted to several successive fusions and crystallizations, and a 
still richer alloy results. 

The alloy thus concentrated is cupelled. The operation con- 
sists in melting the lead in a reverberatory furnace (Fig. 110), 



360 ELEMENTS OF MODERN CHEMISTRY. 

of which the hearth has a hemispherical form, and is called 
the cupel. The vault of the furnace is formed by a sheet-iron 
cover, Gr, which can be raised and lowered at will. When the 
lead is melted, a strong blast of air is blown upon its surface 
through the tuyeres tt ; the lead is thus converted into oxide, 
which melts and, driven by the current of air, flows from the 
cupel through a notch cut in its edge down to the level of the 
molten metal, and which is gradually deepened as that level 
becomes lowered. The silver, which is not oxidizable, becomes 
concentrated in the cupel as the lead is eliminated ; and Avhen 
the last portions of the latter metal become oxidized, the sur- 
face of the silver is covered with only a thin layer of fused 
litharge, which breaks up suddenly and displays the brilliant 
surface of the metal. This phenomenon, called hriglitening^ 
indicates the termination of the operation. 

The oxide of lead formed first in the cupellation of work- 
lead is called ahstricli. It is black, and still contains a little 
silver, as well as copper and antimony (Berthier). The oxide 
which flows out after the abstrich is litharge. 

Properties of Lead. — Lead is a bluish- white metal, having 
a certain degree of lustre when its surface is freshly cut. It 
is the softest and least tenacious of all the common metals. It 
can easily be cut with a knife and scratched by the finger-nail. 
It may readily be reduced to thin sheets, but is not easily drawn 
into wire. Its density is 11.363 (H. Deville). It melts be- 
tween 326 and 334°, and volatilizes at a white heat. It may 
sometimes be obtained crystallized in regular octahedra by 
allowing a large quantity of molten lead to cool slowly, and 
decanting the still liquid portion. 

The brilliant surface of lead tarnishes in the air. When 
melted, it rapidly absorbs oxygen and becomes covered with a 
pellicle of oxide, which is transformed by the prolonged action 
of heat into a yellow powder, known as massicot. 

On contact with aerated water, lead absorbs oxygen and car- 
bon dioxide, and becomes covered with a thin layer of carbon- 
ate. This fact explains the presence of traces of lead in rain- 
water which has been collected from lead gutters, or kept in 
leaden reservoirs. 

The presence of small quantities of sulphates and chlorides 
in water prevents this oxidation of lead, so that the metal can 
be used without danger for the distribution of most spring and 
river waters. 



LEAD MONOXIDE. 361 

Lead is rapidly dissolved by concentrated and boiling hydro- 
chloric acid. Dilute sulphuric acid does not attack it ; the 
boiling concentrated acid converts it into sulphate with evolu- 
tion of sulphurous acid gas. Nitric acid attacks and dissolves 
it at ordinary temperatures, disengaging red vapors and forming 
lead nitrate. 

Lead and its compounds are poisonous. Its effects on the 
economy are especially manifested after the long-continued 
absorption of very small quantities of the metal, of which the 
accumulation in the system is made evident by various symp- 
toms; the best known is lead colic or painter s colic. Plumbers, 
glaziers of pottery, painters, color-grinders, and the workmen 
employed in the manufacture of minium, or red lead, white 
lead, etc., are exposed to this chronic poisoning. The soluble 
sulphates are antidotes for acute cases of poisoning, and potas- 
sium iodide causes the elimination of lead from the system in 
chronic cases. 

Uses of Lead. — This metal is used for the manufacture of 
shot, and pipes for the distribution of water and gas. When 
reduced to sheets it is made into gutters, the coverings of roofs, 
linings for troughs and reservoirs. Sheet-iron dipped into a 
bath of melted lead retains a coating of that metal, and is called 
leaded iron. Lead enters into the composition of type-metal, 
plumber's solder, pewter, etc. 

LEAD MONOXIDE. 

PbO 

Massicot and litharge, of which the formation has been in- 
dicated, constitute the monoxide of lead. 

Massicot is a yellow, amorphous powder. Litharge occurs in 
reddish-yellow, crystalline scales. It is rendered crystalline by 
the fusion and cooling through which it passes. It is sometimes 
met with in the form of rhombic octahedra (Mitscherlich). 

Oxide of lead melts at a red heat ; when fused it absorbs 
oxygen, which it again gives up on solidifying (F. Le Blanc). 

It cannot be melted in an earthen crucible without attacking 
and sometimes piercing the latter, owing to the formation of a 
very fusible silicate of lead. 

Lead monoxide is easily reduced by hydrogen, charcoal, and 
carbon monoxide. 

It is very slightly soluble in water, and possesses a sufficiently 
Q 31 



1 



362 ELEMENTS OF MODERN CHEMISTRY. 

marked alkaline reaction to restore the blue color to feebly 
reddened litmus-paper. 

When potassium hydrate or ammonia is added to a solution 
of a salt of lead, a white precipitate, which is a hydrate of lead, 
is formed. This hydrate dissolves in an excess of potassium 
hydrate ; it is also soluble in lime-water, and these solutions 
are precipitated black by hydrogen sulphide. 

Litharge is used for the manufacture of lead acetate and 
white lead. It gives to linseed oil drying properties. It enters 
into the composition of various plasters, and different coloring 
matters (Cassel's yellow). 

LEAD DIOXIDE. 

Pb02 

This body is made by treating minium, or intermediate oxide 
of lead, with dilute nitric acid. A brown powder remains and 
must be washed with boiling water. This is dioxide of lead ; 
it is insoluble in water ; it is readily decomposed by heat, losing 
half of its oxygen and being converted into monoxide. It is 
an energetic oxidizing agent. When it is briskly triturated 
with a small quantity of sulphur, the latter is inflamed. 

If lead dioxide be introduced into a test-tube filled with sul- 
phurous acid gas, the latter is immediately absorbed with for- 
mation of lead sulphate. 

SO^ + PbO^ = PbSO* 

Hydrochloric acid poured upon lead dioxide determines the 
formation of lead chloride and the disengagement of chlorine. 

PbO^ + 4HC1 = PbCP H- CP + 2ffO 

Lead dioxide unites with the alkalies forming veritable salts. 
Fremy has described a plumbate of potassium, K^PbO^ -}- 
3H^0, which crystallizes in cubes, and which is formed when 
dioxide of lead is gently heated with a very concentrated solu- 
tion of potassium hydrate in a silver crucible. 

PLUMBOSO-PLUMBIC OXIDE (BED LEAD) 

This oxide is prepared by heating massicot in furnaces to a 
temperature that should not exceed 300°. Under these con- 
ditions, the monoxide absorbs oxygen from the air, and is con- 



LEAD SULPHIDE. 363 

verted into a beautiful red powder known as minium or red lead. 
The product obtained by heating lead carbonate or white lead 
in contact with the air is called orange minium. 

Minium is a combination of monoxide and dioxide of lead ; 
its composition is variable, according to the length of time it 
is roasted. It ordinarily corresponds to the formula 

Pb^'O* = 2PbO.PbO^ (Jacquelain) 

Sometimes it contains less oxygen, having the composition 

Pb^O^ = SPbO.PbO^ (Mulder) 

Red crystals of the latter composition have been found in 
the fissures of a minium furnace. 

Minium has a scarlet-red color, which becomes much darker 
on heating. It gives up oxygen at a red heat, being reduced 
to monoxide. If red lead be sprinkled with nitric acid, the 
color disappears, giving place to a brown. The nitric acid 
removes the monoxide, forming nitrate, and leaves the brown 
dioxide. 

Minium is used to color sealing-wax and wall-papers. It is 
employed in the manufacture of flint glass, which owes its fusi- 
bility, its perfect transparency and its refractive power, to sili- 
cate of lead. When mixed with stannic oxide, minium serves 
as an enamel for crockery-ware. 

A mixture of red lead and white lead with a small quantity 
of oil is employed as a luting for steam-pipes, and as a cement. 

LEAD SULPHIDE. 

PbS 

Galena or sulphide of lead occurs in nature in beautiful 
cubical crystals of a bluish-gray color and a metallic lustre ; its 
density is 7.58. It melts at a red heat. When heated in con- 
tact with air, it is converted into oxide and sulphate, and by the 
reaction of an excess of sulphide upon these compounds me- 
tallic lead is produced. Hot fuming nitric acid converts lead 
sulphide into sulphate. Concentrated and boiling hydrochloric 
acid transforms it into chloride with evolution of hydrogen 
sulphide. 

Galena is used for glazing common pottery. A broth of 
powdered galena and cow's dung mixed with water is applied 
to the surface of the previously well-dried vessels. 



364 ELEMENTS OF MODERN CHEMISTRY. 

This sort of pottery is generally baked at a temperature not 
very high, so that the sulphide of lead, the oxidation of which 
is prevented by the cow's dung, melts and spreads over the sur- 
face, forming a varnish of a dark color when cold. Neverthe- 
less, a small quantity of oxide is always formed by the oxidation 
of the galena : when the baking takes place at a higher temper- 
ature, this oxide forms a fusible silicate, which covers the 
pottery. This glazing often has a green color, due to the 
presence of oxide of copper, and is attacked by vinegar and 
other acids, which dissolve the oxides of lead and copper. 
Hence the danger in the use of ware so glazed for culinary 
purposes. 

LEAD CHLORIDE. 

PbCP 

This body may be obtained as a white, crystalline powder by 
heating litharge with hydrochloric acid. If is deposited as a 
dense, white precipitate when hydrochloric acid is added to a 
concentrated solution of acetate or nitrate of lead. It is not 
very soluble in water; 135 parts of water at 12.5°, or 33 parts 
of boiling water being required to dissolve one part of lead 
chloride. It may be obtained crystallized in long needles by 
allowing its saturated boiling solution to cool. Lead chloride 
melts below a red heat, and on cooling solidifies to a semi-trans- 
parent mass, known by the ancient chemists as horn-lead. 

Mineral yellow^ Turner s yellow^ and CasseVs yellow^ em- 
ployed in painting, are oxychlorides of lead, combinations of 
lead oxide and chloride in variable proportions. 



LEAD IODIDE. 

PbP 

When a solution of potassium iodide is added to a solution 
of lead acetate, a beautiful yellow precipitate of lead iodide is 
formed. 

This body melts to a red-brown liquid at a high temperature. 
It requires for solution 1235 parts of cold, or 194 parts of 
boiling water. On the cooling of its saturated, boiling solution, 
it is deposited in golden-yellow, hexagonal scales having a mag- 
nificent lustre. 



LEAD NITRATE — LEAD SULPHATE. 365 

LEAD NITRATE. 

Pb(NO=5)2 

This body is prepared by dissolving litharge in dilute nitric 
acid. It crystallizes from its hot, saturated solution in anhy- 
drous, white, regular octahedra. These crystals decrepitate 
when they are heated; they dissolve in Ti times their weight 
of cold water, and in a much less quantity of boiling water. 

At a red heat this salt is decomposed into nitrogen peroxide, 
oxygen, and lead monoxide. It forms various basic compounds 
with lead monoxide. 

When one molecule of the nitrate is boiled with one molecule 
of the monoxide, and the filtered solution is allowed to cool, 
a crystalline deposit is obtained, which is a dibasic nitrate, 
Pb(NO^)' + Pb 4- H-^0 (Pelouze). This salt can be consid- 
ered as derived from orthonitric acid, H^NO^ = HNO'^ -j~ 
H=^0. Indeed 

Pb(NO^)^ + PbO + R'0 = 2^l NO* 

This basic nitrate of lead corresponds to the basic nitrate of 
bismuth, (page 351). 

Bi'"NO* ^g| NO* 

Bismuth subnitrate. Lead subnitrate. 

When a solution of nitrate of lead is boiled with thin sheet- 
lead, the latter is dissolved, and the liquid assumes a yellow 
color. Under these conditions soluble basic nitrites of lead are 
formed. On cooling the filtered liquid deposits yellow crystals 
having a variable composition. By a prolona^ed boiling a tetra- 
basic nitrite, Pb(NO')' -[- 3PbO + H'^0, is obtained. The so- 
lution of the latter, decomposed by carbon dioxide, gives the 
neutral nitrite Pb(NO^)^ -f- H^O, crystallizing in long, yellow 
prisms (Peligot) or in yellow plates (Chevreul). 

LEAD SULPHATE. 

PbSO* 

This salt is found crystallized in nature. It can be prepared 
by double decomposition by precipitating the solution of any 
soluble lead salt, such as the nitrate or acetate, with sulphuric 
acid or solution of a sulphate. It is a white powder, insoluble 
in water. 

31* 



366 



ELEMENTS OP MODERN CHEMISTRY. 



At a high temperature, lead sulphate melts without decom- 
position. Charcoal reduces it, transforming it into sulphide, 
metal, or oxide, according to the proportions employed. 
Quickly heated with an excess of charcoal, it yields sulphide. 
PbSO^ + C^ = 2C0' + PbS 
By diminishing the proportion of charcoal, a residue of 
metal, or even of oxide, may be obtained. 

PbSO* -f- C r= CO^ + SO^ + Pb 
2PbS0* -f C = CO^ + 2S0^ + 2PbO 
Iron and zinc, in contact with lead sulphate suspended in 
water, cause the separation of metallic lead. 



LEAD CARBONATE. 

PbC03 

Crystallized lead carbonate is found in nature. The salt 
may be obtained artificially, as an amorphous white powder, by 
precipitating a soluble lead salt by an excess of an alkaline 
carbonate. 

A hydrated, and sometimes basic, carbonate of lead is known 
as ceruse or white lead. Its composition varies. 

PbCO^ + H^O and 2PbC0^ + Pb(0H)2 

These are much used in oil painting. White lead is pre- 
pared by several methods, the oldest of which is called the 
Dutch process. It consists in exposing sheets of lead to an 
atmosphere charged with acetic acid 
rsrx- ...........vv.s^v...s..vv.s.^^^^^ ^ vapor and rich in carbonic acid gas. 

The leaden sheets are introduced 
into glazed earthen pots, A (Fig. 
Ill), containing a small quantity of 
vinesar. The lead rests upon short 




projecting arms, B, below which is 
placed the crude vinegar. The 
pots are covered by a disk of lead, 
D, which incompletely closes them. 
Fig. 111. They are then arranged in rows in 

large chambers ; a row of pots is 
placed on a bed of spent tan or horse-manure ; these are cov- 
ered with planks, upon which more spent tan or horse-manure 
is placed, and then another layer of pots, and so on. The fer- 



LEAD CHROMATE. 367 

mentation of the tan or manure raises the temperature to 30 
or 40°, and produces carbonic acid gas. On the other hand, 
the oxygen of the air intervenes, causing the lead to be 
attacked by the acetic acid, so that basic acetate of lead is 
formed upon the surface of the metal ; but this salt is con- 
tinually decomposed by the carbonic acid gas, so that the lead 
gradually becomes covered with a layer of carbonate. 

Thenard suggested another process by which litharge is dis- 
solved in a solution of lead acetate, and a current of carbon 
dioxide passed through the solution of subacetate so formed. 
Lead carbonate is precipitated and neutral acetate regenerated ; 
the latter is then again transformed into basic acetate. The 
product so obtained is known as Clicliy white lead. 

LEAD CHROMATE. 

PbCrO* 

This salt exists crystallized in nature, constituting the red 
lead of Siberia. It is prepared by double decomposition 
between solutions of potassium chromate and lead acetate ; a 
yellow precipitate is thus obtained, and is employed in painting 
under the name chrome yellow. 

Lead chromate melts at a red heat ; at a white heat it loses 
4 per cent, of oxygen. It is easily reduced by charcoal and 
hydrogen. Insoluble in water, it dissolves readily in solutions 
of potassium hydrate. 

Characters of Lead Salts. — The soluble lead salts have a 
sweetish taste. Black precipitates are formed in their solutions 
by both hydrogen sulphide and ammonium sulphide. 

Potassa and soda yield white precipitates, soluble in a large 
excess of the reagent. Ammonia gives a white precipitate, 
insoluble in excess. 

Sulphuric acid forms a white precipitate even in the most 
dilute solutions of lead. Hydrochloric acid forms a white 
precipitate of lead chloride, but this precipitate is not produced 
in dilute solutions. 

Potassium chromate throws down a yellow precipitate, soluble 
in potassium hydrate. 

When heated with sodium carbonate upon a piece of charcoal 
in the reducing flame of the blow-pipe, the lead salts yield a 
metallic globule which when cold can readily be flattened out 
by hammering. 



368 



ELEMENTS OF MODERN CHEMISTRY. 



COPPER. 

Cu (Cuprum) = G3.5 

Natural State. — Copper is found in the native state, some- 
times crystallized in regular octahedra, sometimes in masses. 
It is also found as cuprous oxide, Cu'^0, cupric oxide, CuO, and 
cupric carbonate, CuCO'^ ; but its most abundant minerals are 
cuprous sulphide, Cu^S (Chalkosine), and a double sulphide 
of copper and iron, Cu'^S.Fe^S•^ designated as coppei- pyrites. 
Under the name gray copper are also worked various minerals 
containing cuprous sulphide combined with the sulphides of 
antimony and arsenic, and in which the copper is sometimes 
replaced by iron, zinc, silver, and mercury. 

Treatment of Copper Ores. — Copper is easily extracted 
from cuprous oxide and cupric carbonate. These ores are 
melted with charcoal in suitable furnaces, and the metal is at 
once obtained. Copper pyrites, which is often mixed with 
cuprous sulphide, requires a more complicated treatment. The 
iron and sulphur must be eliminated, and for this reason the 
ore is subjected to an incomplete roasting. This operation is 
conducted in a reverberatory furnace (Fig. 112). The flame 




of the fire sweeps the arched vault of the furnace vv. The 
opening of the chimney is at C, and the ore is fed in from iron 
troughs placed above the furnace. 



COPPER. 369 

The first roasting drives out part of the sulphur, and the 
sulphides of iron and copper are partially converted into oxides 
and sulphates. An excess of sulphide remains, and the im- 
perfectly-roasted ore is fused in presence of silicious materials. 
The scoriae formed in roasting the matt (see farther on) are 
generally added, and sometimes fluor spar, to render the slag 
more fusible. This operation is conducted either in cupola-fur- 
naces or in reverberatory furnaces of peculiar construction. In 
presence of the unattacked sulphide of iron, the cupric oxide 
formed during the roasting is converted into cupric sulphide, and 
oxide of iron is formed. The latter unites with the silica, as 
does also the oxide produced by the roasting, both being reduced 
to ferrous oxide by the reducing gases of the fire. Ferrous sili- 
cate is thus formed, and constitutes a very fusible slag, below 
which accumulates the sulphide of copper containing much less 
sulphide of iron than the original pyrites. This product is the 
matt. 

The sulphur, which was thus far necessary to expel the iron, 
must now be removed, and the matt is broken up and repeat- 
edly roasted, by which the remainder of the iron is oxidized and 
nearly all of the sulphur expelled. The mineral is now again 
melted with silicious materials and the scorias produced in re- 
fining black copper, and rich in cupric oxide, are added. Ferrous 
silicate separates as a slag, and a metallic mass containing from 
90 to 94 per cent, of copper, still alloyed with iron, lead, 
arsenic, sulphur, etc., is obtained. This product constitutes 
hlack copper. 

Refining of Black Copper. — The impure metal is melted in 
a reverberatory furnace ; the oxygen of the air transforms the 
copper into oxide, and the latter is gradually reduced by the 
foreign metals and the sulphur still contained in the mass of 
copper ; these oxides separate in the form of scoriae and slags, 
which are removed. The li(j[uid copper collects in a cylin- 
drical cavity in the furnace, where it is solidified by throwing 
cold water upon the surface of the molten metal ; it is then 
removed in the form of disks, and is called rosette cojoper. 
The copper thus obtained is brittle, owing that property to the 
cupric oxide with which it is still impregnated. It is finally 
melted under a layer of charcoal, and stirred with poles of green 
wood. 

Hed, ductile copper is thus obtained. 

At Mansfeld, in Prussia, a copper pyrites is worked which 




370 ELEMENTS OF MODERN CHEMISTRY. 

is disseminated in little crystals in an argillaceous scliist impreg- 
nated with bitumen. After a series of roastings and smeltings, 
a black copper is obtained, rich enough in silver to permit of 
the advantageous extraction of that metal. For this purpose 
the method called liquation is employed. The argentiferous 
copper is melted with lead, and the liquid alloy is allowed to 
cool slowly. Copper solidifies first, alloyed with a small quan- 
tity of lead, while the remainder of the lead, retaining nearly 
all of the silver, remains liquid. By another process the alloy 
of lead and argentiferous copper is made into disks, D (Fig. 113), 

and these are reheated very slowly. 
As soon as the temperature is suf- 
ficiently high, the lead melts and 
runs out, carrying with it all of the 
silver. The copper remains al- 
loyed with a small quantity of lead. 
It is refined by melting it in a cu- 
pola-furnace under the blast of a 
Fig. 113. tuyere. The lead and iron and 

part of the copper are oxidized, 
and the oxides are removed as scoriae. Pure copper remains 
and is converted into rosette. The argentiferous lead is sub- 
mitted to cupellation, as already described. 

Cement copper is copper precipitated from a solution of 
cupric sulphate by metallic iron. It is very pure. 

Properties of Copper. — This metal has a characteristic red 
color that is universally known. When rubbed with the hand 
it exhales a peculiar, disagreeable odor. By fusion it crystal- 
lizes in cubes, but it may be deposited by electrolysis in reg- 
ular octahedra. It melts towards 1100°, and maybe volatilized 
by the heat of the oxy-hydrogen blow-pipe. 

Its density varies from 8.85 to 8.95. It is very malleable, 
ductile, and tenacious. 

In dry air it is unaltered at ordinary temperatures, but it 
absorbs oxygen in presence of moisture and carbonic acid gas. 
Green spots are then formed upon the surface of the metal, 
constituting a hydrocarbonate of copper ; this is the product 
ordinarily called verdigris. 

At a high temperature copper absorbs oxygen with avidity, 
being converted into black, cupric oxide if the oxygen be in 
excess ; but in the contrary case, red, cuprous oxide is formed. 
The oxidation is favored by division of the metal. 



CUPROUS OXIDE. 3*71 

If some pulverulent copper, produced by the decomposition 
of copper acetate, be thrown upon a moderately hot tile and an 
incandescent coal be approached so as to heat one point, a black 
spot instantly forms there and rapidly extends throughout the 
mass, showing the progress of the oxidation. 

In presence of acids or ammonia, copper rapidly absorbs 
oxygen at ordinary temperatures. 

If some ammonia and copper-turnings be shaken up with air 
in a glass-stoppered bottle, the ammoniacal liquid becomes blue ; 
if now the bottle be turned upside-down and opened under 
water, the latter will rise in the bottle, replacing the oxygen 
which was absorbed. The blue liquid contains in solution am- 
moniacal oxide of copper and nitrite of copper (Schonbein, 
Peligot). 

This liquid is capable of dissolving cotton and lint, which 
are almost pure cellulose (Schweizer). 

"When heated with concentrated sulphuric acid, copper is 
converted into sulphate with disengagement of sulphurous 
acid gas. Nitric acid, even dilute, dissolves it readily, forming 
cupric nitrate and evolving nitrogen dioxide. Boiling hydro- 
chloric acid attacks it slowly, disengaging hydrogen and forming 
cuprous chloride. 

Uses of Copper. — Copper is much employed for the con- 
struction of boilers, alembics, stills and worms, and for kitchen 
utensils. Sheet-copper is used for coating the bottoms of ships 
and sometimes for roofing houses. This metal enters into the 
composition of the more important alloys, brass (copper and 
zinc), bronze (copper and tin), German silver (copper, zinc, and 
nickel). 

CUPROUS OXIDE. 

This oxide is found in nature, sometimes in vitreous masses, 
sometimes in beautiful, red, regular octahedra. 

It is ordinarily prepared in the wet way by boiling a solution 
of acetate of copper with glucose ; a bright-red, crystalline pow- 
der is precipitated, which is anhydrous cuprous oxide. When 
heated in contact with air, it absorbs oxygen and is converted 
into cupric oxide. 

When potassium hydrate is added to a solution of cuprous 
chloride, a yellow precipitate of cuprous hydrate is thrown 
down. Cuprous oxide is used to communicate a red color to glass. 



372 ELEMENTS OF MODERN CHEMISTRY. 



CUPRIC OXIDE. 

CuO 

Two processes are used for the preparation of this important 
body : calcination of copper in the air ; calcination of cupric 
nitrate. The first method furnishes a granular, compact, black 
oxide ; the second, a fine, deep-black powder. 

Cupric oxide is easily reduced by both hydrogen and char- 
coal, with formation of either water or carbon dioxide. 

With water it forms a hydrate, Cu(OH)' = CuO.H'^O, which 
precipitates as a thick, light-blue magma, when potassium hy- 
drate is added to a cupric solution. This hydrate is converted 
into brown, anhydrous oxide by boiling with water. Cupric 
oxide is largely used in the laboratory in the analysis of or- 
ganic substances. It is used in the arts to color glass, to which 
it imparts a green color. 

SULPHIDES OF COPPER. 

Copper forms two sulphides, corresponding to the oxides. 
Ciiprous snlpMde, Cu^S, occurs in nature in fusible, steel-gray 
crystals, which may be scratched with a knife. 

CiqJTic sulphide CuS, is formed in the wet way when a 
solution of a copper salt is precipitated by hydrogen sulphide. 
When strongly calcined, it loses sulphur and is reduced to 
cuprous sulphide. 

If copper filings or turnings be thrown into a flask containing 
boiling sulphur, a brilliant incandescence takes place from the 
union of the two elements. 

CHLORIDES OF COPPER. 

Cuprous chloride, Cu^CP, is prepared by boiling copper- 
turnings in hydrochloric acid and adding small quantities of 
nitric acid from time to time. The nitro-muriatic acid formed 
converts the copper into cupric chloride, which is reduced by 
the excess of copper present. A brown liquid is thus obtained 
which, by continued boiling, becomes almost colorless. On 
adding water to this liquid, a white, crystalline precipitate of 
cuprous chloride is deposited. It is insoluble in water, but dis- 
solves in aqueous ammonia, forming a liquid which remains 
colorless when kept in closed vessels in presence of an excess 



CUPRIC SULPHATE. 373 

of copper, but becomes blue on exposure to the air, from wliich 
it absorbs oxygen. 

Carbon monoxide is perfectly absorbed by a solution of 
cuprous chloride in hydrochloric acid or in ammonia. 

Cu.pric chloride, CuCl'^, is obtained by dissolving cupric oxide 
in hydrochloric acid or in aqua regia. A green solution is 
formed, which, after concentration, deposits beautiful rhombic 
prisms of a bluish-green color, containing 2 molecules of water 
of crystallization. 

CUPRIC SULPHATE. 

CuSO* + 5H20 

Preparation. — This salt is commonly called blue vitriol. It 
is a product of many industrial operations, such as roasting 
sulphurous copper ores, and the decomposition by copper of 
the silver sulphate resulting from the refining of gold, — that 
is, the treatment of silver coin containing gold with sulphuric 
acid. 

Cupric sulphate produced by roasting copper ore contains 
more or less ferrous sulphate. The two salts crystallize together 
in oblique rhombic prisms, containing 7 molecules of water of 
crystallization. The mixture is called Salzburg vitriol. 

Instead of copper pyrites, artificial cupric sulphide may be 
oxidized. Old copper plates are moistened and sprinkled with 
flowers of sulphur; they are then heated in a furnace, and the 
sulphide of copper first formed is converted into sulphate by 
the oxygen of the air drawn into the furnace. The still hot 
plates are plunged into water, which dissolves the layer of cupric 
sulphate, and the same operation is repeated until all of the 
metal is transformed into sulphate. 

The simplest process consists in boiling copper turnings and 
clippings with sulphuric acid : sulphurous acid gas is disen- 
gaged, and cupric sulphate formed. In the arts, the operation 
is conducted in wooden tanks lined with lead and heated by 
steam. 

Properties. — Cupric sulphate crystallizes in parallelopipedons 
belonging to the type of the dissymetric prism. These crystals 
have a fine blue color, and contain 5 molecules of water. When 
exposed to dry air they effloresce .superficially : heated to 100°, 
they lose 4 molecules of water, disengaging the fifth only at 
243°. The anhydrous salt is white. At a high heat, cupric 



374 ELEMENTS OF MODERN CHEMISTRY. 

sulphate is decomposed into cupric oxide, sulphurous oxide, 
and oxygen. 

Cupric sulphate dissolves in 4 parts of cold, and in 2 parts 
of boiling water, and the concentrated solution has a pure blue 
color. It is insoluble in alcohol. 

When an excess of ammonia is added to a solution of cupric 
sulphate, a beautiful, dark-blue liquid is obtained. It contains 
ammoniacal cupric sulphate, CuSO^ -|~ 4NH^ -f- H'^0, which 
separates in dark-blue crystals when alcohol is added to the 
aqueous solution. 

There are several basic sulphates of copper representing 
compounds of cupric sulphate and cupric hydrate. One of 
them is obtained as a green powder when a solution of cupric 
sulphate is digested with cupric hydrate. The bluish precipi- 
tates obtained by incompletely precipitating solutions of cupric 
sulphate with potassium hydrate are basic sulphates. 

XJses. — Cupric sulphate is employed as a caustic applicable 
to diseases of the eye. In the arts, it is used in the prepara- 
tion of blue ashes, a mixture of calcium sulphate and cupric 
hydrate, made by decomposing cupric sulphate with milk of 
lime. 

It is much used in dyeing, particularly in dyeing black on 
wool and cotton. Its solution is used for steeping wheat. 
Large quantities of sulphate of copper are employed for elec- 
trotyping. 

CARBONATES OF COPPER. 

When cold solutions of sodium carbonate and cupric sul- 
phate are mixed, a bluish-green precipitate is obtained, and at 
the same time carbonic acid gas is disengaged. The precipi- 
tate becomes gTeen when washed with warm water. It is 
known as mineral green, and can be regarded as a combina- 
tion of one molecule of cupric carbonate with one molecule of 
cupric hydrate. It contains 

CuCO^ + Cu(0H)2 

A similar compound exists in nature, constituting malacliite. 
This mineral occurs in green masses. When cut and polished, 
it presents veins of various tints, and is fashioned into orna- 
mental objects, such as vases, cups, etc. 

Azurite or mountain blue, which crystallizes in beautiful, 



CARBONATES OF COPPER. 375 

blue, oblique rhombic prisms, can be regarded as a compound 
of two molecules of cupric carbonate with one of the hydrate. 

2CuC0^ + CuCOH)^ 

Debray has reproduced azurite artificially by leaving calcium 
carbonate for a long time in contact with cupric nitrate in 
sealed tubes. 

ALLOYS OF COPPER. 

Brass is an alloy of copper and zinc, ordinarily containing i 
zinc and | copper. It often contains a small proportion of tin 
and even of lead. 

Bronze is an alloy of copper and tin (see table of alloys, page 
237). While brass is malleable and ductile, bronze is brittle 
when it has been slowly cooled, but it becomes malleable after 
tempering, — that is, when it is heated to redness and then 
plunged into cold water. 

Gi-erman silver contains 25 per cent, of zinc, 25 of nickel, 
and 50 of copper. 

Characters of Copper Salts. — These salts are blue or green. 
Their solutions are precipitated brown by hydrogen sulphide 
and ammonium sulphide ; an excess of the latter reagent will 
not dissolve the precipitate. 

Potassium hydrate forms a dense, light-blue precipitate, in- 
soluble in excess. Ammonia first forms a pale-blue precipitate, 
which is then dissolved by an excess of the reagent with a rich 
sky-blue color. 

Potassium ferrocyanide gives a chestnut-brown precipitate 
even in very dilute cupric solutions. 

An apple-green precipitate of cupric arsenite (Scheele's 
green) is formed when potassium arsenite is added to cupric 
sulphate. 

A bright piece of iron plunged into a cupric solution in- 
stantly becomes covered with a deposit of metallic copper. 



MERCURY. 

Hg (Hydrargyrum) = 200 

Natural State and Extraction. — Mercury occurs native, 
and especially combined with sulphur, mercuric sulphide or 
natural cinnabar being its principal ore. It is found in differ- 



376 



ELEMENTS OF MODERN CHEMISTRY. 



ent localities in Europe and America, principally at Almaden, 
Spain; Idria, in Illyria; San Jose, in California. 

The treatment of the ore is very simple. The sulphide is 
roasted in a current of air in furnaces of peculiar construction : 
the sulphur is oxidized, and passes off as sulphur dioxide, the 
mercury being set free. The metal volatilizes and is led, to- 
gether with the gases from the combustion, either into con- 
densation-chambers, or through long rows of little cylindrical 
vessels, where the mercury condenses. 

Fig. 114 represents the furnaces employed at Almaden, 
with the fireplace, and the body, AB, charged with ore. The 




Fig. 114. 

mercury-vapor passes by o, and condenses in a series of aludels 
entering one in the other, and arranged upon two inclined planes, 
ah, he. ^ The condensed metal runs into a channel, 6, from 
which it is conducted into a reservoir. The sulphurous acid 
gas, still charged with vapor of mercury, passes into a chamber, 
C, descending to the floor, where it is cooled by contact with a 
trough filled with water, d. In this chamber the condensation 
of the mercury-vapor is completed. 

Fig. 115 represents the several-storied furnaces aa, hh, cc, 
and the condensation-chambers CC, used at Idria. 

Cinnabar may also be reduced by iron or by lime. 

The metal thus extracted is purified by filtration through 
ticking-cloth or chamois-skin. It is ordinarily transported in 
forged iron bottles. 

The mercury of commerce is nearly always alloyed with small 
quantities of other metals, such as lead, tin, copper, and bis- 



MERCURY. 



377 



muth. In this state its surface is not as brilliant as when pure, 
it does not run as readily, and the drops are drawn out to a 
point. They are said to form tails. It may be purified by dis- 
tillation, an operation which requires certain precautions, and 
which is ordinarily effected in the iron bottles which serve for 
the transportation of the metal. 

It may also be purified by digesting it for several days with 
one-thirtieth its weight of commercial nitric acid diluted with 
its own weight of water; the aqueous liquid is then decanted 
and the mercury washed, first with warm water acidulated with 
nitric acid, then with pure water, after which it can be dried. 
In this operation, the nitric acid removes the foreign metals, 
more oxidizable than the mercury, which displace the latter 
metal from its solution in the nitric acid. 




Fig. 115. 

Properties. — Mercury is liquid, but solidifies at — 40°. The 
solid metal at this low temperature is malleable, and has a 
density of 14.4. The density of liquid mercury is 13.595. It 
boils at 350° of an air thermometer. Its vapor is colorless, 
and has a density of 6.976. 

It is unaltered by contact with the air at ordinary tempera- 
tures, but at 300° it slowly absorbs oxygen, and its surface 
becomes covered with a red powder, which is mercuric oxide, 
called by the ancients red precipitate. 

Mercury combines with chlorine, bromine, and iodine at ordi- 
nary temperatures, and with sulphur by the aid of a gentle heat. 

32- 



378 ELEMENTS OF MODERN CHEMISTRY. 

Hydrochloric acid does not attack it. Dilute nitric acid dis- 
solves it in the cold, forming mercurous nitrate. Hot nitric 
acid dissolves it, forming mercuric nitrate and evolving red 
vapors. 

OXIDES OF MERCURY. 

Two oxides of mercury are known, mercurous oxide, Hg^O, 
and mercuric oxide, HgO. 

The first is prepared by digesting mercurous chloride (calo- 
mel) with potassium hydrate; a black powder is obtained which 
is very unstable. By the action of light, or by a temperature 
above 100°, it decomposes into mercuric oxide and mercury. 

Mercuric Oxide, HgO, can be obtained by either the dry or 
wet method. The first consists in decomposing mercuric nitrate 
by heat ; the salt is gradually heated in a flask on a sand- 
bath until red vapors cease to be disengaged. 

The oxide thus prepared is an orange-red, granular, and 
crystalline powder. 

Mercuric oxide is prepared in the wet way by decomposing 
a solution of mercuric chloride by potassium hydrate. A 
yellow precipitate of anhydrous mercuric oxide is obtained. 

When mercuric oxide is heated, it assumes a dark-red color 
and decomposes, if the temperature be above 400°, into ox3^gen 
and mercury. It yields its oxygen to many bodies, such as 
charcoal, sulphur, and phosphorus, which it oxidizes energet- 
ically. When heated with sulphur, it produces an explosion. 
In these reactions the finely-divided yellow oxide is more active 
than the red oxide. 

MERCURIC SULPHIDE. 

HgS 

This is the cinnabar generally found in nature in compact 
masses, sometimes in transparent, red, hexagonal prisms or 
rhombohedra. It is manufactured by directly combining sul- 
phur and mercury. The combination takes place when the 
bodies are triturated together in the cold, in the proportion of 
100 parts of mercury and 18 parts of sulphur. A black mass 
is thus obtained which is sublimed in iron vessels. 

Cinnabar prepared by sul)limation occurs in dark-red masses, 
having a fibrous and crystalline structure. Its density is 8.124. 
At a high temperature, it volatilizes without melting. When 



MERCUROUS CHLORIDE. 379 

heated in the air, it burns with a blue flame, yielding sulphur- 
ous acid gas and metallic mercury. It is decomposed by hydro- 
gen, charcoal, and most of the metals. Boiling sulphuric acid 
decomposes it with formation of sulphurous acid gas and sul- 
phate of mercury. Nitric acid scarcely attacks it, even when 
boiling. 

Vermillion is a finely-divided mercuric sulphide having a 
rich scarlet color. It is prepared by triturating foi* several 
hours in a mortar, 300 parts of mercury and 114 parts of 
flowers of sulphur, and adding to the black sulphide thus ob- 
tained 75 parts of potassa and 400 parts of water. The mixture 
is maintained at a temperature of about 45°, being continually 
triturated with a pestle. As soon as the powder has acquired 
a fine scarlet color, it is rapidly washed with hot water and 
dried. It is employed in painting and also to color sealing- 
wax. 

MERCUROUS CHLORIDE, OR CALOMEL. 

Hg2C12 

Mercurous chloride is largely used in medicine under the 
name calomel or mild chloride of mercury . 

Preparation. — An intimate mixture of mercurous sulphate 
and sodium chloride is heated in a capacious glass matrass on 
a sand-bath. The mercurous chloride, formed by double decom- 
position, sublimes. 

Hg^SO* -f 2NaCl = Hg^CP + Na^SO* 

It is thus obtained in compact, crystalline masses. When 
it is strongly heated and its vapor passed into large stoneware 
vessels filled with steam, it condenses in an impalpable powder, 
in which form it is used by preference in medicine. 

Calomel may also be prepared in the wet way by adding 
hydrochloric acid, or a solution of sodium chloride, to a solu- 
tion of mercurous nitrate. A white, curdy precipitate is 
obtained which is washed and dried. 

Properties. — Prepared in the dry way calomel occurs as 
dense, fibrous, crystalline and slightly transparent masses, one 
side of which is smooth, the other presenting the sharp points 
of the crystals. When exposed to light, it becomes yellow and 
even gray in time, being partially decomposed. Its density is 



380 ELEMENTS OF MODERN CHEMISTRY. 

7.17. The density of its vapor is 8.85. It melts and vola- 
tilizes at the same temperature. When slowly sublimed, it 
crystallizes in square prisms. It is insoluble in water. 

A solution of potassium iodide agitated with calomel con- 
verts it into a green powder of mercurous iodide. If an excess 
of potassium iodide be employed, the green powder disappears 
and is replaced by a gray precipitate of metallic mercury, the 
mercurous iodide at first formed being decomposed into mercury 
and mercuric iodide, which dissolves in the potassium iodide. 

An analogous reaction takes place with the alkaline chlorides 
by the aid of heat, the mercurous chloride breaking up into 
mercuric chloride which dissolves, and metallic mercury which 
is deposited. 

MERCURIC CHLORIDE, OR CORROSIVE SUBLI- 
MATE. 

HgC12 

Preparation. — This body is obtained by double decomposi- 
tion, by heating a mixture of mercuric sulphate and sodium 
chloride on a sand-bath. The mercuric chloride condenses in 
the upper part of the matrasses which are imbedded up to the 
neck in the sand. 

HgSO^ + 2NaCl = Na^SO* + HgCP 

Towards the close of the operation the heat is increased in 
order to agglomerate the sublimate by a partial fusion. 

Another process consists in passing chlorine into heated 
mercury ; the combination takes place with the production of 
luminous heat. 

Properties. — Mercuric chloride prepared by the dry method 
occurs in compact, white, crystalline and friable masses, having 
a density of 6.5. It is an energetic poison. It melts at about 
265°, and boils towards 295°. The density of its vapor is 
9.42. By sublimation it may be obtained crystallized in rec- 
tangular octahedra. 

It is soluble in 1 9 parts of cold water, also in alcohol and ether. 
It is deposited from its hot, saturated, aqueous solution in 
long prisms, belonging to the type of the right rhombic prism. 
The crystals are anhydrous. 

The aqueous solution of mercuric chloride produces a white 
precipitate in a solution of albumen of white of egg. This 



MERCUROUS IODIDE — MERCURIC IODIDE. 381 

precipitate is a combination of mercuric chloride and albumen. 
Albumen is thus the antidote to corrosive sublimate. 

When a slight excess of ammonia is added to a solution of 
corrosive sublimate, a white deposit is formed, known as ivhite 
precipitate, of which the composition is expressed by the 
formula HgH'^NCl. 

HgCP + 2NH^ = NH^Cl + HgffNCl 

It may be regarded as the chloride of mercury-ammonium, 
that is, ammonium chloride in which 2 atoms of hydrogen are 
replaced by one atom of the diatomic metal mercury. 

HgH'NCl = H f NCI 
H S 

Corrosive sublimate forms crystallizable double combinations 
with the alkaline chlorides and with ammonium chloride. 



MERCUROUS IODIDE. 

Hg2I2 

This compound is ordinarily prepared by directly combining 
mercury and iodine. 100 parts of mercury and 63.5 parts of 
iodine are triturated with a small quantity of alcohol, until the 
whole is converted into a green powder, which is then washed 
with boiling alcohol and dried. 

It may also be prepared by double decomposition by precipi- 
tating a solution of mercurous nitrate with potassium iodide, 
or by the reaction of the latter body upon calomel. 

Mercurous iodide is not a stable compound. It is decom- 
posed by light. Heat breaks it up into mercury and mercuric 
iodide, and the same decomposition is eiFected by potassium 
iodide and the alkaline chlorides. 

MERCURIC IODIDE. 

HgP 

Mercuric iodide is prepared by pouring a solution of 100 
parts of potassium iodide into a solution of 80 parts of corro- 
sive sublimate. A beautiful scarlet-red precipitate of mercuric 
iodide is thrown down. 

It is necessary that the bodies be employed in the propor- 



382 ELEMENTS OF MODERN CHEMISTRY. 

tions indicated ; an excess of potassium iodide would dissolve 
the mercuric iodide first precipitated. 

Mercuric iodide is almost insoluble in water ; it is slightly 
soluble in boiling alcohol, which deposits it on cooling in small 
red octahedral crystals. 

If mercuric iodide be heated in a small glass retort, it melts 
to a dark-yellow liquid which solidifies on cooling to a yellow 
mass. At a higher temperature the liquid boils and its vapor 
condenses in a dark-yellow liquid which solidifies to a yellow 
mass ; at the same time, right' rhombic prisms of a yellow color 
sublime. If these be rubbed with a glass rod or other hard 
body they instantly become red, first at the point of contact, 
then throughout the entire mass. 

These two forms of mercuric iodide constitute one of the 
most curious examples of dimorphism. 

Mercuric iodide forms a combination with potassium iodide 
which is soluble in water. A solution of this iodo-hydrargyrate 
of potassium is not precipitated by potassium hydrate, but the 
liquid rendered alkaline by the latter reagent is a very sensi- 
tive test for ammonia (^Nesslers test), with which it gives a pre- 
cipitate or a brown cloud more or less intense, according to the 
quantity of ammonia present. 

NITRATES OF MERCURY. 

Neutral mercuroiis nitrate (Hg')"(NO^)' + 211^0, is ob- 
tained by the action of an excess of cold, dilute nitric acid upon 
metallic mercury. After some time, short colorless prisms are 
formed in the liquid, constituting the neutral salt. The latter 
is readily soluble in water charged with nitric acid. 

When mercury is attacked by an excess of boiling nitric 
acid and the solution is evaporated, voluminous crystals of a 
basic mercuric nitrate separate, Hg(NO^)MIgO -j- 2H^0. 

The syrupy liquid from which these crystals are deposited, 
contains neutral mercuric nitrate. 

Hg(NO^0' + 8H^0 

This salt is deposited in large, colorless, rhombic tables when 
the syrupy solution is cooled to — 15°. 

A large quantity of cold water decomposes this nitrate intQ 
nitric acid Avhich dissolves, and a basic salt, Hg(NO'^)^2HgO 
-f- H^O, forming a yellow powder. 



SULPHATES OF MERCURY. 383 

SULPHATES OF MERCURY. 

There is a mercurous sulphate, (Hg^)"SO^, and a mercuric 
sulphate, Hg"SO^ 

The first is obtained by heating equal parts of mercury and 
sulphuric acid, arresting the operation when two-thirds of the 
mercury are converted into a white, crystalHne powder. Mer- 
curous sulphate is but slightly soluble in cold water. 

To prepare mercuric sulphate, 1 part of mercury and IJ 
parts of sulphuric acid are heated to complete desiccation on a 
sand-bath. 

Hg + 2H^S0* = 2H^0 + HgSO* -f SO^ 

It is well to add a small quantity of nitric acid before drying. 

Mercuric sulphate is an anhydrous, white powder. It decom- 
poses at a red heat into metallic mercury, sulphurous acid gas, 
and oxygen. Charcoal reduces it readily, equal volumes of 
carbon dioxide and sulphur dioxide being disengaged. 

Mercuric sulphate is slightly soluble in water : a large quan- 
tity of cold water converts it into a yellow, basic salt, HgSO*. 
2HgO, known as turpeth mineral. 

Characters of Mercurous Salts. — Their solutions are pre- 
cipitated black by hydrogen sulphide, and also by potassium 
hydrate and ammonia. Hydrochloric acid gives a white pre- 
cipitate which is blackened by ammonia. Potassium iodide 
forms a green precipitate of mercurous iodide, converted by 
an excess of the reagent into mercuric iodide which dissolves, 
and gray metallic mercury. 

Characters of Mercuric Salts. — Solutions of mercuric salts 
are precipitated black by an excess of hydrogen sulphide, and 
by ammonium sulphide. 

Potassium hydrate forms a yellow precipitate, insoluble in 
excess. 

Ammonia yields a white precipitate in solutions of corrosive 
sublimate. 

Hydrochloric acid does not precipitate the mercuric salts. 

Iron, zinc, and copper precipitate metallic mercury from 
both mercurous and mercuric solutions. A slip of copper 
dipped into such solutions becomes covered with a gray coating 
which acquires brilliancy by rubbing. 

Heated with lime in a glass tube, all of the mercury com- 
pounds yield metallic mercury which sublimes in small globules. 



384 



ELEMENTS OF MODERN CHEMISTRY. 



easy to recognize under the microscope, and which can be char- 
acterized by the addition of iodine, the vapor of which converts 
the metallic globules into yellow or red mercuric iodide. 



SILVER. 

Ag(Argentum) = 108 

Natural State. — Silver is found native and in combination 
in many minerals. Among these are the sulphide, the sulph- 
antimonides and sulpharsenides, the antimonide, chloride, bro- 
mide, iodide, selenide, telluride, and lastly an amalgam of 
silver. It is found in small proportions in many galenas and 
copper pyrites. 

Treatment of Silver Ores. — The silver is extracted from 
galena by first reducing the lead, and then submitting the 
argentiferous lead obtained to cupellation (page 359). 

Silver ores free from lead are treated by a peculiar process 
called amalgamation^ since it is based upon the employment 
of metallic mercury which dissolves silver; the amalgam of 
silver formed is decomposed by heat. 

Several processes are employed for the chlorination and 
amalgamation of silver. 

Freiberg Amalgamation Process. — The Freiberg silver ore 
is poor, containing only two or three thousandths of silver in 
the form of sulphide, disseminated 
through iron and copper pyrites. 
The ore is pulverized, mixed with 
one-tenth its weight of common 
salt, and roasted in a reverberatory 
furnace. The sulphides are oxi- 
dized, with disengagement of sul- 
phurous acid gas and formation of 
sulphates. The latter react upon the 
sodium chloride, forming sodium 
sulphate and metallic chlorides : all 
of the silver is thus converted into 
chloride. The product of the roast- 
ing is reduced to powder, washed, 
and introduced, together with water and scrap-iron, into amal- 
gamation barrels, which are rotated by water-power (Fig. 116). 
When the mixture has become homogeneous, mercury is added 




Fig. 116. 



SILVER. 



385 




Fig. 117. 



and dissolves the silver set free by the action of the iron upon 
the silver chloride ; it also dissolves a small quantity of copper 
formed by the reduction of cuprous chloride present. After 
the barrels have been rotated for some hours, the amalgam is 
collected and compressed in canvas bags, through which the 
excess of mercury, alloyed with a very small quantity of 
foreign metals, passes, while a pasty _ 

amalgam of silver and copper remains 
in the bags. This amalgam is put into 
iron cups, hh (Fig. 117), set upon an 
iron rod on a tripod base, a, standing in 
a vessel of water. The whole is cov- 
ered with a bell-shaped iron hood which 
dips into the water, and the upper part 
of which is surrounded by burning 
coals. The mercury volatilizes and 
condenses in the cold water, and an 
alloy of silver and copper, containing 
about 28 per cent, of the latter metal, 
as well as small quantities of lead, 
antimony, etc., remains in the cups. 
It is purified either by cupellation or by refining. 

Cupellation consists in melting the impure silver with lead, 
as has been already described. In refining, the silver is melted 
in a hemispherical iron vessel lined with a thick layer of marl 
and wood ashes. It is a porous cupel, which absorbs the oxides 
formed by the action of the air upon the lead and copper 
alloyed with the silver ; the latter remains in the cupel at the 
close of the operation in a pure state. 

Mexican Amalgamation Process. — American silver ore con- 
sists of sulpharsenide and sulphantimonide of silver, mixed with 
silver chloride and native silver, the whole being disseminated 
in silica, calcium carbonate, and ferric oxide. In Mexico, the 
following primitive process is still used. The finely-pulverized 
ore is mixed with two per cent, of common salt and thrown 
into circular areas paved with flag-stones, where it is rendered 
homogeneous by being trodden for several hours by mules. 
About one per cent, of copper pyrites which has been roasted 
in the air and contains cupric sulphate is then added. The 
latter salt reacts with the sodium chloride, forming sodium sul- 
phate and cupric chloride, which latter decomposes the silver 
sulphide, forming silver chloride and cupric sulphide. Mer- 
R 33 



386 ELEMENTS OF MODERN CHEMISTRY. 

curj is then added and reduces the silver chloride, with for- 
mation of chloride of mercury and metallic silver. During the 
whole time the mass is continuall}^ trodden by the mules, and 
the mercury comes in contact with the disseminated silver : the 
amalgam formed solidifies in about a fortnight. A second and 
finally a third addition of mercury is then made until 7 or 8 
parts of that metal have been employed for one part of silver 
to be extracted. After a few months, the operation is termi- 
nated, and the mass is washed v/ith large quantities of water to 
remove the earthy and salty matters. The amalgam remains, 
and is heated in order to extract the silver. 

American Process. — The above method of extraction is too 
slow to be employed for the vast quantities of silver ore that 
are mined on the Pacific Slope. The ore is there crushed and 
roasted with sodium chloride and a small proportion of cupric 
sulphate, in furnaces of a peculiar construction. By this means 
all of the silver is converted into chloride. The mass is made 
into a pulp with water and agitated with mercury in large tanks 
or vats. The silver chloride is reduced as before, and the 
amalgam obtained is first squeezed out and afterwards heated 
in iron retorts to expel the mercury. 

Properties. — Silver is the whitest and most brilliant of all 
the ordinary metals. Next to gold, it is the most malleable 
and the most ductile. Its density is 10.5. 

It melts towards 1000°, and when fused has the curious 
property of dissolving oxygen, of which it absorbs 22 times its 
volume. On solidifying, it again disengages the gas ; this phe- 
nomenon, which occasionally causes the projection of portions 
of silver, is called spitting. Silver volatilizes at the high tem- 
perature of the oxyhydrogen blow-pipe. 

It is unaltered by the air. It absorbs ozone, being converted 
into the dioxide Ag^O^ It combines with hydrogen dioxide, 
forming argentous and argentic hydrates (Weltzien). 

It decomposes concentrated solution of hydriodic acid, dis- 
engaging hydrogen and forming silver iodide (Deville). Hy- 
drochloric acid only attacks it superficially. Hydrogen sulphide 
blackens it, forming a pellicle of silver sulj)hide. Its best sol- 
vent is nitric acid which attacks it in the cold, yielding silver 
nitrate and disengaging red vapors. 

The alkalies have no action upon silver; for this reason, silver 
vessels are used for fusing potassium hydrate and concentrating 
its solution. 



SILVER SULPHIDE — SILVER CHLORIDE. 387 



SILVER OXIDE. 

Ag^O 

The only important oxide of silver is the monoxide, which 
is precipitated in the anhydrous state when potassium hydrate, 
free from chloride, is added to a solution of silver nitrate. 

It forms an olive-brown, flocculent deposit which yields a 
brown powder on drying. 

Silver oxide is readily decomposed by heat into silver and 
oxygen. It is reduced by hydrogen at a temperature below 
100°, When recently precipitated, it is slightly soluble in 
water. It is an energetic base, perfectly neutralizing the acids, 
and displacing cupric oxide from the cupric salts. 

When oxide of silver is digested with ammonia it is con- 
verted into a very explosive, black powder, known as fulmi- 
nating silver. Its composition is not yet well known. 

SILVER SULPHIDE. 

Ag^S 

To the oxide of silver corresponds the sulphide Ag^S, which 
occurs native, crystallized in regular octahedra, ordinarily mod- 
ified by facettes. It is soft and can be scratched by the finger- 
nail. Silver and sulphur also combine readily by the aid of 
heat. 

SILVER CHLORIDE. 

AgCl 

This body is found native and is known to mineralogists as 
horn-silver. It is sometimes found crystallized in cubes and 
octahedra. It is formed directly when silver is heated in chlo- 
rine gas, and is prepared by double decomposition by adding 
hydrochloric acid or a solution of sodium chloride to solution 
of nitrate of silver. A white, curdy precipitate is thus obtained, 
which assumes a violet tint when exposed to the action of light. 
The change of color is due to partial decomposition. 

Silver chloride melts at about 260°, and solidifies on cooling 
to a gray, horn-like mass that can be cut with a knife. 

If recently precipitated and moist silver chloride be placed 
upon a sheet of zinc, in a short time a dark color will appear 
on the borders of the chloride, and the whole of that body will 



388 ELEMENTS OF MODERN CHEMISTRY. 

soon be converted into a dark-gray powder of finely-divided 
silver. Zinc chloride is at the same time formed. 

This reaction takes place much more rapidly if the silver 
chloride be moistened with hydrochloric acid. In this case 
the reduction is effected by nascent hydrogen produced by the 
action of the hydrochloric acid on the zinc. 

When silver chloride is fused with the alkaline hydrates or 
carbonates, it is reduced to metallic silver : oxygen is disen- 
gaged, and an alkaline chloride is formed. 

llecently-precipitated silver chloride dissolves readily in aque- 
ous ammonia. When dry, it absorbs ammonia gas abundantly, 
and Faraday employed this compound for the preparation of 
liquid ammonia. 

Silver chloride dissolves also in solutions of the alkaline 
hyposulphites. 

SILVER IODIDE. 

Agl 

Silver iodide is obtained as a yellow precipitate by adding 
potassium iodide to a solution of silver nitrate. It blackens 
on exposure to light. It is but very slightly soluble in ammo- 
nia, a property which distinguishes it from silver chloride. 

SILVER NITRATE. 
AgN03 

This salt is prepared by dissolving silver in nitric acid. If 
the metal be pure, a colorless solution is obtained which after 
concentration and cooling deposits large, colorless tables of an- 
hydrous silver nitrate. If silver coin be employed, the solution 
will be blue, containing, independently of silver nitrate, cupric 
nitrate. The latter may be removed by evaporating the residue 
to dryness and carefully heating it, so that the salt may remain 
fused for some time. The cupric nitrate is decomposed, while 
the silver nitrate remains mixed with cupric oxide, frym which 
it may be freed by solution and filtration. 

Fused silver nitrate constitutes lunar cavsfic. 

This salt dissolves in its own weight of cold, and in half its 
weight of boiling water. The solution is neutral to test-paper. 
When exposed to the air, it blackens, as do also the crystals 
and the fused salt, by reason of a partial reduction due to the 
organic matters suspended in the air. 



ASSAYING OF SILVER. 389 

It blackens the skin from a similar cause. 

Hydrogen slowly reduces the solution of silver nitrate with 
deposition of metallic silver (Beketoff). 

Characters of Silver Salts. — Solutions of the silver salts 
are precipitated black by hydrogen sulphide and by ammonium 
sulphide. 

Potassium hydrate forms an olive-green precipitate of silver 
oxide, insoluble in excess. Ammonia does not precipitate them. 

Hydrochloric acid and the soluble chlorides form a white 
precipitate of silver chloride, insoluble in either cold or boiling- 
nitric acid, but soluble in ammonia. 

Potassium iodide gives a yellow precipitate, almost insoluble 
in ammonia. 

Silvering. — This operation consists in covering the common 
metals or glass with a coating of silver more or less thick. 

The metals are silvered by either amalgamation or galvanic 
deposition. In the latter and preferable operation, a solution 
of the double cyanide of silver and potassium is generally used. 

Mirrors and glass articles in general are silvered by the re- 
duction of a silver salt by aldehyde, glucose, or tartaric acid. 
The following receipt is given by Liebig: a solution of 10 
grammes of silver 'nitrate is supersaturated with ammonia and 
rendered strongly alkaline by caustic soda. The volume of 
the liquid should be 1450 c.c. Another solution is prepared 
by dissolving 1 part of milk sugar in 10 parts of water. The 
latter solution is mixed with its own volume of the first solu- 
tion, and the glass to be silvered is washed with alcohol and 
immersed in the liquid. The reduction of the silver salt begins 
immediately, and does not require the aid of heat. 

The experiment may easily be made in a glass flask, the 
interior of which will be uniformly silvered. 

Assaying of Silver. — This name is applied to the methods 
which serve for the analysis of alloys of silver and copper, such 
as coin, medals, silverware, and jewelry. The assay may be 
conducted by the dry way or by the wet way. 

The dvy assay consists in the operation called cvpellation 
(Fig. 118). A certain quantity of metallic lead is melted in 
a cupel of bone-ash in a reverberatory furnace, and a weighed 
quantity of the alloy of silver and copper, carefully wrapped 
in a small piece of paper, is placed upon the fused metal. The 
silver dissolves in the melted lead, and a ternary alloy is thus 
obtained which is exposed to the action of air at a red heat. 

33* 



390 



ELEMENTS OP MODERN CHEMISTRY." 



Under these conditions, the lead and copper become oxidized ; 
the oxide of lead fuses, and the melted litharge, which should 
be in great excess in proportion to the oxide of copper, dis- 
solves the latter, and with it is absorbed by the porous cupel. 
The phenomenon of brightening (page 360) indicates the ter- 
mination of the process. 




Fig. 118. 

The wet assay ^ invented by Gay-Lussac, consists in adding 
to a solution in nitric acid of a known weight of the alloy of 
silver and copper, a titered solution of sodium chloride, that 
is, a solution containing an exactly known weight of salt in one 
litre of water. This solution is cautiously added until it no 
longer precipitates silver chloride, and the quantity of silver 
present is calculated by the volume of the titered solution that 
has been required to completely precipitate the silver in the 
form of chloride. As the latter readily deposits from a liquid 
that is carefully agitated, it is easy to catch the termination 
of the operation, that is, the precise moment when all of the 
silver is precipitated and the addition of the titered liquid 
must be arrested. 



GOLD. 391 

Process. — Two titered solutions are used to precipitate the 
silver: 1st, a normal solution, containing 0.5417 gramme of 
sodium chloride per decilitre, a quantity sufficient to precipitate 
one gramme of silver ; 2d, a decuiormal solution, that is, one 
containing the same quantity of sodium chloride per litre, so 
that 1 c.c. of this liquid will precipitate one milligramme 
of silver. To analyze an alloy of silver, a coin, for example, 
such a quantity is weighed as would contain one gramme of 
silver, if the proportion of silver were a little less than the 
extreme limit allowed. If the alloy ought to contain 900 
thousandths of pure silver, with a tolerance of 2 thousandths, 
it would be rejected should it contain only 897 thousandths. 

We suppose, however, that the latter is its quality, and 
weigh a quantity of the alloy which would then contain one 
gramme of pure silver, that is, 1.1148 grammes. This alloy 
is dissolved in nitric acid, and one decilitre of the normal solu- 
tion is added. All of the silver should not be precipitated, for 
the standard of the alloy should be above 897. This is deter- 
mined by adding to the clarified liquid one or more cubic cen- 
timetres of the decinormal solution, until the liquid ceases to 
be troubled by a fresh addition. As each cubic centimetre of 
this solution corresponds to one milligramme of silver, we must 
add to the gramme of silver at first precipitated as many 
milligrammes as we have added cubic centimetres of the deci- 
normal solution, the last cubic centimetre added counting for 
only half a milligramme. Knowing the quantity of pure silver 
contained in 1.1148 grammes of the alloy analyzed, the 
standard of the latter is determined by a simple calculation. 



GOLD. 

Au(Aurum) = 197 

Natural State. — Gold is one of the most anciently known 
metals. It is generally found in the native state, either in 
streaks or veins, or in sand. It ordinarily occurs in scales or 
rounded grains disseminated in alluvial sands, or in the rocks 
whose disintegration produces such sands. It is well known 
that gold-dust is suspended in the waters of certain rivers. 

Gold is sometimes found combined with silver, lead, copper, 
and tellurium. 



392 ELEMENTS OF MODERN CHEMISTRY. 

Extraction. — Gold is extracted from auriferous sand by 
washings, which remove the particles lighter than the gold. 
These washings are conducted in wooden troughs (cradles), or 
on inclined tables, the gold sinking to the bottom of the cradles 
or remaining on the tables. When it is in particles too minute 
to be separated mechanically from the sand, which still remains 
in small quantity, the whole is agitated with mercury ; the gold 
dissolves. The amalgam thus obtained is compressed in a 
chamois-skin, which allows the passage of the excess of mer- 
cury. When the solid residue is distilled the gold remains. 

Auriferous quartz rocks are crushed to powder, which is then 
subjected to washings. Mercury is sometimes employed to ex- 
tract the gold from the pulverized rock. The following process 
has been employed for some years in California and Australia. 
The crushed rock, with mercury, water, and two cast-iron balls, 
is introduced into basins, to which a rotating motion is given 
(Fig. 119). By the friction of the balls it is soon reduced to 




Fig. 119. 

an impalpable powder, which remains suspended in the water, 
and is carried out with the latter through openings in the upper 
part of the basins, while the gold amalgamates with the mer- 
cury. 

Native gold, as well as that extracted from different minerals, 
is nearly always alloyed with silver. The two metals are sep- 
arated by the wet way, by attacking the alloy with either nitric 
or sulphuric acid. Nitrate or sulphate of silver is formed, the 
latter being soluble in hot water. The gold remains in a pul- 
verulent state. It is to be remarked that the alloy of gold and 
silver must be rich in silver in order that this process, called 
refining, can be applied. Hence it is sometimes necessary to 



OXIDES OF GOLD — CHLORIDES OF GOLD. 393 

increase the proportion of silver by melting tlie alloy with that 
metal. 

An alloy of gold and silver rich in gold may also be treated 
with aqua regia. Both metals are converted into chlorides; 
that of silver is insoluble, while that of gold dissolves. When 
ferrous sulphate is added to the yellow solution of chloride of 
gold, a precipitate of metallic gold is obtained, the chlorine 
acting upon the iron of the ferrous sulphate which is thus 
transformed into ferric salt. 

Properties of Gold. — Pure gold has a beautiful yellow color. 
In thin leaves it is translucent, allowing the passage of a green- 
ish light. Its density is 19.5. It is quite soft, and is the most 
malleable and most ductile of the metals. 

It melts at 1200°, and volatilizes at a higher temperature. 
Its vapor is gTeen. 

It is unaltered by the air at all temperatures. Sulphuric, 
hydrochloric, nitric, and phosphoric acids have no action on it 
either in the cold or when aided by heat. It is dissolved by 
nitro-hydrochloric acid. 

Some gold leaf may be boiled with hydrochloric acid in a 
test-tube ; the gold will resist the action of the acid, and will 
retain its lustre. Some more gold leaf may be boiled with pure 
nitric acid in another tube, and again the metal will not be 
attacked. But on mixing the two liquids, the gold will be dis- 
solved with disengagement of red vapors. Gold trichloride will 
be formed, and will color the liquid yellow. 

OXIDES OF GOLD. 

There are two compounds of gold and oxygen, a monoxide, 
Au^O, and a trioxide, Au^Ol The latter forms compounds 
with the bases. When magnesia is added to solution of auric 
chloride, an insoluble yellow precipitate of magnesium aurate 
is formed ; when this is decomposed by nitric acid it leaves auric 
hydrate. This hydrate is yellow ; it easily parts with its water, 
and is converted into a brown-black powder of auric oxide. 
The latter is not stable, being decomposed by light and by a 
temperature of about 250°. 

CHLORIDES OF GOLD. 

Aurous chloride, AuCl, is obtained as an insoluble yellow 
powder by heating auric chloride to 230°. 



394 ELEMENTS OF MODERN CHEMISTRY. 

Auric chloride or trichloride of gold, AuCP, is prepared by 
dissolving the metal in aqua regia. After concentration the 
liquid solidifies, on cooling, to a dark-red, crystalline and deli- 
quescent mass. 

The solution of auric chloride is yellowish-brown when con- 
centrated, pure yellow when dilute. It is decomposed by light. 
It colors the skin violet, and is reduced by a great number of 
bodies. Phosphorus, and hypophosphorous, phosphorous and 
sulphurous acids precipitate from it metallic gold. It is the 
same with most of the metals, which combine with the chlorine, 
setting free the gold. A brown precipitate of metallic gold is 
immediately obtained on adding a solution of ferrous sulphate 
to a solution of auric chloride. Auric chloride dissolves in 
ether, which removes it from its aqueous solution when the 
two liquids are agitated together. 

If a solution of auric chloride be added to a mixture of 
stannous and stannic chlorides in solution, a flocculent precipi- 
tate of a purple color, more or less pure according to the con- 
centration of the solutions and the proportions of the mixture, 
will be formed. It is purple of Cassiiis, a compound employed 
in painting on glass and porcelain. It contains tin, gold, oxy- 
gen, and hydrogen, but its constitution is not well known. 

Auric chloride forms crystalline compounds with the alkaline 
chlorides. When a mixture of chloride of gold and sodium 
chloride is evaporated until a pellicle forms on its surface, yellow 
crystals containing NaCl. AuCP -|- 2H^0, are formed on cooling. 

Gilding. — Several processes are used for gilding metals, such 
as silver and copper. The objects may be gilded by amalga- 
mation, by dipping, or by galvanic deposition. 

Gilding hy Amalgamation. — Grold readily alloys with mer- 
cury, and the amalgam is used for gilding objects of silver and 
copper. The pieces are heated to destroy greasy matters, and 
are then cleaned by dipping them into dilute sulphuric acid, 
after which they are washed and dried with saw-dust. They 
are then rubbed with a brush of brass wires dipped into a solu- 
tion of mercurous nitrate, and then with a brush impregnated 
with an amalgam of one part of gold and eight parts of mer- 
cury. They are afterwards heated to volatilize the mercury, 
an operation dangerous to the health of the workmen, and which 
should be conducted in a furnace having a good draught. The 
pieces thus gilded are dull ; they become lustrous after suitable 
washings and polishings. 



PLATINUM. 395 

Gilding hy Dipping. — Copper objects may be covered with 
a thin film of gold by dipping them into a boiling solution of 
carbonate and phosphate of sodium to which auric chloride 
has been added. 

Electro- Gilding. — The copper objects, previously heated and 
cleaned by dilute sulphuric acid, are plunged for a few seconds 
into dilute nitric acid and then wiped dry. They are then 
connected with the negative pole of a battery and dipped into 
a bath composed of 1 part of cyanide of gold, 10 parts of potas- 
sium cyanide, and 100 parts of water. A plate of gold plunged 
into the same bath constitutes the positive pole. When the 
current passes, the objects become covered with a uniform and 
adherent coating of gold. As the metal is precipitated from 
the solution, it is replaced by an equivalent quantity from that 
which constitutes the positive pole, and which dissolves. The 
bath thus retains a constant composition. The same process 
is applicable to electro-silvering. 

Assaying of Gold Alloys. — Gold is assayed by cupellation. 
The alloy is first melted with silver, so that the quantity of the 
latter metal present may be at least triple that of the gold. 
This alloy is submitted to cupellation, an operation which 
presents no dijB&culty, for gold rich in silver does not spit. 
The button is hammered out to a thin sheet, reheated and 
formed into a little cornet, which is introduced into a small 
flask and heated with nitric acid of 22° Baume. After several 
minutes' boiling the greater part of the silver is dissolved ; the 
liquid is then decanted and replaced by more concentrated nitric 
acid. All of the silver dissolves and the gold remains in the 
form of a but slightly coherent cornet. It is washed, heated to 
redness in a crucible to give it coherence, and finally weighed. 



PLATINUM. 

Pt = 197.5 

Natural State and Treatment of Platinum Ores. — Plat- 
inum is found native, generally in alluvial sands. Its principal 
deposits are in the Ural Mountains, Brazil, and New Granada. 
The platinum ore, extracted from the sand by washing, contains, 
independently of 73 to 86 per cent, of platinum, various other 
metals, such as iridium, palladium, rhodium, osmium, ruthenium, 
gold, iron, and copper ; an alloy of osmium and iridium, and 



396 ELEMENTS OF MODERN CHEMISTRY. 

various minerals, such as titaniferous iron, chrome iron, pyrites, 
etc. The ore is well washed to remove the sand, and treated 
with dilute aqua regia which dissolves the gold, iron, and cop- 
per; it is then heated with concentrated hydrochloric acid and 
nitric acid is gradually added. The aqua regia dissolves the 
platinum and certain of its accompanying metals, leaving the 
osmium and iridium. The solution is neutralized with sodium 
carbonate and treated with a solution of cyanide of mercury, 
which precipitates palladium cyanide. A solution of ammo- 
nium chloride is added to the filtered liquid, and forms an 
abundant precipitate of ammonium and platinum double chlo- 
ride, which is generally mixed with a small quantity of ammo- 
nium and iridium double chloride. This precipitate is calcined 
at a dull-red heat, and leaves a dull-gray, spongy residue. It 
is spongy platinum. It contains a small quantity of iridium. 

To give coherence to this sponge and convert it into a mal- 
leable and ductile metal, it is reduced to powder in a wooden 
mortar and triturated with enough water to convert it 'into a 
perfectly homogeneous paste. This paste is introduced into a 
slightly-conical cylinder of brass or iron, and compressed first 
with a wooden piston, then by a steel rod. The compression 
is finished by the aid of a hydraulic press, and the slightly- 
conical cylinders so formed are heated to whiteness and forged 
under the hammer, as iron is forged. 

H. Sainte-Claire Deville and Debray have recently extracted 
the metal by simple fusion of the ore. The fusion is effected 
in a lenticular cavity cut in two large masses of quick-lime, 
placed one above the other. A current of illuminating gas is 
directed into this furnace, and the combustion is supported by 
a continual supply of oxygen. 

Properties of Platinum. — Platinum has a grayish-white 
lustre. It melts only at the highest attainable temperatures. 
The density of the cast metal is 21.1 ; that of the forged metal 
21.5. It softens at a white heat, and can then be forged and 
welded like iron. 

The experiments of H. Deville and Troost have shown that a 
red-hot platinum tube allows hydrogen to pass through its pores. 

Platinum has the curious property of condensing gases on its 
surface, and this property is the cause of certain chemical phe- 
nomena that were formerly attributed to mere contact of the 
metal. 

If a morsel of platinum-sponge be introduced into a small 



CHLORIDES OF PLATINUM. 397 

jar filled with an explosive mixture of oxygen and hydrogen, 
the gases will combine instantly, with explosion. 

This property is most highly developed in platinum-hlach, 
for in this form the metal exists in an extreme state of 
division. It may be prepared by reducing a solution of 
platinic chloride by zinc; or platinum dichloride may be boiled 
with potassium hydrate, and alcohol or a solution of sugar 
gradually added to the liquid, which must be continually 
stirred. The platinum is precipitated as a black powder. 

Platinum is unaltered by the air. It is not attacked by 
either nitric, hydrochloric, or sulphuric acids, even boiling. It 
dissolves in aqua regia. The alkaline hydrates attack it at high 
temperatures on contact with the air. It is the same with the 
alkaline nitrates. 

There are two oxides of platinum, a monoxide, PtO, and a 
dioxide, PtO'^ 

CHLORIDES OF PLATINUM. 

These are the more important compounds of platinum. 
There are two, a dichloride, PtCP, and a tetrachloride, PtCl*. 

Platinum dichloride is obtained by cautiously heating the 
tetrachloride to 200^. Chlorine is disengaged, and after cool- 
ing, the residue is exhausted with boiling water, which leaves 
an olive-green powder, constituting the dichloride. When 
ammonia is added to a solution of platinum dichloride in 
hydrochloric acid, a green, crystalline powder separates after 
some time. It is called green salt of Magnus^ and contains 

PtCP + 2NH3 

It may be regarded as the dichloride of platinoso-diammonium. 

Pt" ^ 



H^ 
H^ 
H^ 



NICP 



It is derived from two molecules of ammonium chloride by 
the substitution of an atom of diatomic platinum for two atoms 
of hydrogen. 

Platinum tetracMoride, or platinic chloride, PtCl*, is 
formed when platinum is dissolved in aqua regia. A red- 
brown solution is obtained, which, after concentration and cool- 
ing, deposits red-brown needles of hydrated platinic chloride. 

34 



398 ELEMENTS OF MODERN CHEMISTRY. 

The crystals lose their water when heated, and are converted 
into a dark, red-brown mass, which constitutes the anhydrous 
chloride PtCl*. This body absorbs moisture when exposed to 
the air. It is very soluble in water, alcohol, and ether. 

If a solution of ammonium chloride be added to a solution 
of platinic chloride, a yellow, crystalline precipitate of plati- 
num and ammonium double chloride is immediately formed. 
This body is but little soluble in cold water, but more soluble 
in boiling water, from which it is deposited in microscopic, 
regular octahedra. It is almost insoluble in alcohol. It contains 

PtCP.2NH^Cl 

A yellow, crystalline precipitate of double chloride of plati- 
num and potassium is obtained, in the same manner, on adding 
a solution of platinic chloride to a solution of a potassium salt, 
if the liquids be not too dilute. 

PtC1^2KCl 



> 



ORGANIC CHEMISTRY. 



GENERAL IDEAS UPON THE CONSTITUTION 
OF ORGANIC COMPOUNDS. 

Organic chemistry studies the history of the compounds 
of carbon. The most simple of these are the gases carbon 
monoxide and carbon dioxide ; each contains but a single atom 
of carbon. In this respect they resemble the inflammable gas 
which is disengaged from the mud of marshes ; it contains one 
atom of carbon combined with four atoms of hydrogen. 

The gas hydrogen diearbide or ethylene, which has already 
been mentioned, contains two atoms of carbon united with four 
atoms of hydrogen. A great number of compounds are known 
which contain only carbon and hydrogen, and they are called 
hydrocarbons or carburetted hydrogens. The atoms of carbon 
are aggregated in them, together with the atoms of hydrogen. 
Other elements are often added to the preceding, forming 
molecules more or less complex. The carbon atoms form as it 
were the framework, and the carbon compounds possess pecu- 
liar properties precisely on account of the easy facility with 
which the atoms of carbon accumulate in one and the same 
molecule, and link themselves in some manner one to another. 
The following developments will give some idea of the mode 
of generation and the structure of organic molecules. 

The most Simple Organic Compounds. — Their Composi- 
tion proves Carbon to be a Tetratomic Element. — The most 
simple of the hydrocarbons is marsh gas. 

When this gas is submitted to the action of chlorine, one or 
more atoms of hydrogen may be removed from it ; they com- 
bine with the chlorine and are disengaged in the form of hy- 
drochloric acid gas. The curious fact, first noticed by Dumas, 
is then observed, that each atom of hydrogen which is removed 
is replaced by an atom of chlorine. This suhstitution gives 

399 



400 ELE3IENTS OF MODERN CHEMISTRY. 

rise to a series of chlorinated compounds, which present the 
most simple relations with marsh gas. The latter contains only 
carbon and hydrogen. The chlorine compounds derived from 
it by substitution, form with it the following series : 

CH* marsh gas, or methane. 

CH^Cl monochloromethane (methyl chloride). 

CH^Cl^ dichloromethane (methylene chloride). 

CHOP trichloromethane (chloroform). 

CCl* tetrachloromethane (carbon tetrachloride). 

In each of these compounds a single atom of carbon is united 
with four monatomic atoms. We have seen that the atoms of 
chlorine and hydrogen are equivalent as regards their power 
of combination. In the preceding compounds, the sum of the 
atoms of h3^drogen and chlorine which are combined with one 
atom of carbon is invariably four, and this number cannot be 
exceeded. But two atoms of a monatomic element may be re- 
placed by one atom of a diatomic element. One atom of car- 
bon, which unites with four atoms of hydrogen or chlorine, 
may unite with two atoms of oxygen to form carbon dioxide 

CO"^ 

and this compound is saturated like those preceding, for one 
atom of oxygen is equivalent to two atoms of hydrogen or 
chlorine. In carbon monoxide, CO", the affinity of carbon is 
not satisfied ; hence this gas will unite directly with an atom 
of oxygen to form carbon dioxide, or with two atoms of chlo- 
rine to form chloro-carbonic gas. 

CO"CP 

In ammonia, one atom of nitrogen is combined with three 
atoms of hydrogen ; nitrogen is triatomic ; hence it may replace 
three atoms of hydrogen. A body is known which represents 
marsh gas, in which three atoms of hydrogen are replaced by 
one atom of nitrogen. This is the dangerous poison known as 
prussic or hydrocyanic acid, and the composition of which is 
represented by the formula 

CN'"H 

In all of the compounds which have just been mentioned a 
single atom of carbon is invariably united to a number of ele- 
ments of which the united atomicitias is always four, and never 
more nor less than that number. It is then reasonable to 
conclude that in them carbon plays the i^civt of a tetratomic 



INTRODUCTION TO ORGANIC CHEMISTRY. 401 

element. This important fact, first exposed by Kekule, can be 
clearly understood if we represent the preceding atomic formulas 
in a graphic manner, that is, by symbols so arranged as to show 
the reciprocal relations of the atoms and their mutual satura- 
tion. In these formulae a saturated atomicity is indicated by 
a line of union, two atomicities by two lines, etc. 

H H H CI 

H-C-H H-C-Cl Cl-C-Cl Cl-C-Cl 

H H CI CI 

Mai'sh gas, Monochloro- Trichloromethane, Carbon 

uiethaae. (Chloroform.) tetrachloride. 

CI 
0=C=0 C1-C=0 H-C^N 

Carbon dioxide. Cblorocarbonic gas. Hydrocyanic acid. 

There exists a very volatile, ethereal liquid, which represents 
marsh gas, in which one atom of hydrogen is replaced by iodine. 
It is the body known as methyl iodide, CH^I. 

If this body be heated for a long time in a sealed tube with 
a solution of potassium hydrate, potassium iodide will be grad- 
ually formed, and the solution will contain a volatile, spirituous 
liquid which can easily be separated by distillation, for it boils 
at 66°. It is the same body which constitutes the most vola- 
tile of the liquids which are formed in the destructive distilla- 
tion of wood ; it is called wood spirit, and its chemical name is 
methylic alcohol. 

The reaction by which it is formed is very simple. The 
iodine of the methjd iodide combines with the potassium ; but 
when this iodine is removed, the carbon remains united to but 
three atoms of hydrogen. It is no longer saturated, and it 
therefore combines with the oxygen and hydrogen which were 
united with the potassium in the potassium hydrate. 

CH^I + KOH = CHIOH + KI 

It will be seen that the atom of oxygen alone does not com- 
bine with the group CH'^, which is called methyl. It is accom- 
panied by an atom of hydrogen, with which it remains united 
in the new compound which is called methyl hydrate or 
methylic alcohol. As has been said, this oxygen replaces the 
iodine in the iodide of methyl, but as it possesses two atomici- 
ties, and the carbon already united with H^ has only one free 
atomicity, the atom of oxygen can only fix upon the carbon by 

34- 



402 ELEMENTS OF MODERN CHEMISTRY. 

one of its atomicities ; the other remains saturated by the atom of 
hydrogen. The latter is then drawn into the combination, and is 
united, not to the carbon, but to the oxygen. The reaction takes 
place as if the atom of iodine were replaced by the group liy- 
droxyl (OH) which is monatomic. Hence the relations between 
the atoms in methyl hydrate are represented by the formula 

H 

H-C-(OH)' 

H 

If we compare the constitution of the three bodies CH^Cl, 
CH^I, CH\OH), we notice that they contain a common ele- 
ment, namely, the group CH^, which is united to chlorine, to 
iodine, or to hydroxyl. Besides this, experiment has shown 
us that methyl iodide can be transformed into hydrate. The 
group methyl hence presents a certain stability and can pass 
from one combination to another. This is expressed by saying 
that it is a radical. 

If methyl iodide be heated with an aqueous solution of 
ammonia, among the products formed will be found the hydri- 
odide of a base which represents ammonia in which one atom 
of hydrogen is replaced by the group methyl. Potassium 
hydrate sets this base at liberty. At ordinary temperatures 
and pressures, it constitutes a gas, very soluble in water and 
possessing a strong ammoniacal odor. It is methylamine. The 
reaction by which it is formed is as follows : the iodine with- 
draws one atom of hydrogen from the ammonia, which atom 
of hydrogen is replaced by the group CII^. 

CH^I + NH^ ^ CH^(NH2).HI. 

Methylamine hydriodide. 

In methylamine then, the fourth atomicity of the carbon 
atom is saturated by nitrogen, but as this element is triatomic 
it brings into the combination two atoms of hydrogen which 
saturate its two other atomicities. It may then be said that 
in methylamine the fourth atomicity of carbon is saturated by 
the group NH'^ This is expressed in the following formulas. 

H H 

H-C-Nr:H^ = H-C-(NH2)' 

Methylamine. 



INTRODUCTION TO ORGANIC CHEMISTRY. 403 

Generation of Hydrocarbons containing Several Atoms 
of Carbon. — The preceding compounds contain but a single 
atom of carbon, but starting with one of these compounds we 
may produce more complicated organic molecules containing 
several carbon atoms. 

If methyl iodide be heated with sodium in sealed tubes, 
sodium iodide is formed, and a gas, a hydrocarbon, is confined 
under great pressure in the tubes. This gas escapes, and may 
be collected, when the drawn-out points of the tubes are opened 
in the blow-pipe flame. It is dimethyl, and has been formed 
according to the following reaction : 

2CW1 -f Na^ = C-'H« -}- 2NaI 

Methyl iodide. Dimethyl, or ethane. 

Two molecules of methyl iodide have entered into the reac- 
tion, and the whole of the carbon of these two molecules is 
found in one molecule of the hydrocarbon, C-H^ = (CH^)^, 
which results. 

On losing their iodine the two methyl groups combine to- 
gether. One of the carbon atoms attracts the other, exchanging 
with it the fourth atomicity set free by the loss of the iodine. 
Hence the iodine of one of the molecules of methyl iodide has 
been replaced by the carbon of the other, which fixes upon the 
group CH^ by a single one of its atomicities, and at the same 
time brings into the combination the three atoms of hydrogxin 
which saturate the other three atomicities. This is expressed 
in the following formuli^ : 

H ^ H H H 

H-C-H H-C-I H-C-C-H 

I I II 

H H HH 

Methane (methyl hydride). Methyl iodide. Dimethyl (ethyl hydride or ethane). 

The mode of generation of this new hydrocarbon, which 
contains two atoms of carbon, is worthy of consideration. It 
results from the substitution of a methyl group for one atom of 
hydrogen in methyl hydride. One atom of carbon, accompa- 
nied by three atoms of hydrogen, fixes upon another atom of 
carbon of which it completes the saturation. By this exchange 
of atomicities each of the carbon atoms retains only three afiin- 
ities which are satisfied by three atoms of hydrogen. The 
two methyl groups, CH^ -\- Cff := C'H^, are then united by 
their carbon atoms, and are held together by the affinity of 



404 ELEMENTS OF MODERN CHEMISTRY. 

carbon for carbon. In methyl hydrate the group hydroxyl is 
bound to the group CH^ by the affinity of carbon for oxygen. 
In methylamine, the group NH'"^ is united to the group CH^ by 
the affinity of carbon for nitrogen. In dimethyl, it is carbon 
which is united to carbon. This has before been expressed by 
saying that the atoms of this element possess a faculty to accu- 
mulate in one and the same molecule. 

It is in this curious property that must be sought the reason 
for the existence of those innumerable compounds, more or less 
rich in atoms of carbon, which constitute the immense field of 
organic chemistry. 

But it is important to study by new examples this mode of 
formation of organic compounds. 

Dimethyl, which we have seen is produced by the action of 
sodium upon methyl iodide, is also known as ethyl hydride. If 
one of its atoms of hydrogen be replaced by an atom of chlo- 
rine, ethyl chloride, C^H^Cl, is obtained. Ethyl iodide, C'-^H^I, 
represents ethyl hydride, in which one atom of hydrogen has 
been replaced by iodine. 

If a mixture of methyl iodide and ethyl iodide be heated 
with sodium, among the products of the reaction will be found 
a gas containing C'^H^ ; it is the methylide of ethyl, resulting 
from the combination of methyl, CH^, with the group ethyl, 
C^H^. It represents ethyl iodide in which the atom of iodine 
has been replaced by a methyl group, the carbon of the latter 
group being fixed by one of its atomicities to one of the carbon 
atoms of the group C"H^. 

In the same manner, by heating a mixture of propyl iodide, 
C^H'I, and methyl iodide with sodium, we may add to the 
propyl group, C^H^, a new atom of carbon escorted by its three 
atoms of hydrogen. 

HH HHH HHHH 

II III I I I I 

H-C-C-I H-C-C-C-H H-C-C-C-C-H, etc. 

II III I I I I 

HH HHH HHHH 

Ethyl iodide. Methyl-ethyl (propane). Methyl-propyl (biitane). 

Nothing prevents the continuation of these additions of car- 
bon to incomplete hydrocarbons, that is, to the residues of the 
subtraction of iodine from the saturated iodides, of which the 
following are the names and formulae : 

CH^I C^H^I C^H'I C^H^I C^H"I, etc. 

Methyl iodide. Ethyl iodide. Propyl iodide. Dutyl iodide. Amyl iodide. 



INTRODUCTION TO ORGANIC CHEMISTRY. 405 

. The following hydrocarbons would then be formed succes- 
sively : 
CH3-CH3 C2H5-CH3 C3H7-CH3 C*H9-CH3 CSHii-CH^, etc. 

Methyl-methyl Methyl-etliyl Methyl-propyl Methyl-butyl Methyl-amyl 
(Ethane). (Propane). (Butane). (Pentane). (Hexane). 

In all of these cases, the atoms of carbon united together 
form, as it were, a continued chain, and the atoms of hydrogen 
are grouped around them as satellites. 

Homologous Bodies. — Very simple relations exist between 
the hydrocarbons of which we have just studied the mode of 
formation. They form a series of which each member differs 
from the preceding by the addition of CHI These relations 
will appear clearly if the formulge already given be replaced 
by the crude formulae : 

C H* methane. 
C'W ethane. 
C^H^ propane. 
C'W butane. 
cm'' pentane. 

This group of hydrocarbons constitutes what is called the 
homologous series of marsh gas, or the series C"H"^"+'^ 

Many other series are known, the terms of which are related 
to each other in the same manner, and the bodies which form 
part of them may present the greatest differences in composition. 
Sometimes they contain only carbon and hydrogen. Again, 
they may contain oxygen or nitrogen in addition to these ele- 
ments ; in this case the former elements are united to carbon by 
one or more of their atomicities, as has already been indicated. 

In any organic body whatever, if an atom of hydrogen united 
with carbon be replaced by a methyl group, CH^, the superior 
homologue of that body is obtained, that is, the compound which 
differs from the original body by the addition of CH^ There 
is a great resemblance in physical and chemical properties 
between such homologues. 

Some of these homologous series will be indicated farther on. 

Immediate Principles and Chemical Species. — The four 
elements, carbon, hydrogen, oxygen, and nitrogen, are the more 
ordinary elements of organic compounds. Those which are 
found in nature in the organs of plants and animals, and which 
have been called by Chevreul immediate principles, contain 
no others, excepting sulphur, which exists in certain of them. 



406 ELEMENTS OF MODERN CHEMISTRY. 

But nearly all of the other elements can be introduced artificially 
into organic compounds ; it is thus with bromine, iodine, phos- 
phorus, arsenic, boron, silicon, and a great number of the metals. 

In uniting with carbon, in dilFerent manners and in various 
proportions, these elements form an innumerable multitude of 
compounds, each of which has a fixed composition and definite 
properties. These bodies constitute the clieinical species^ so to 
say. When submitted to the action of reagents, all may be 
modified in a thousand manners, and transformed into each 
other. Sometimes their composition is simplified, one or more 
carbon atoms being removed from the chain. Sometimes it is 
complicated by the addition of new atoms of carbon. 

All of these bodies contain carbon, and are distinguished 
from each other : 

1. By the number of carbon atoms contained in the molecule. 

2. By the nature and arrangement of the other atoms com- 
bined with the carbon. 

3. By the arrangement of all of the atoms in the molecule. 

The facts relative to the atomic composition of organic com- 
pounds are obtained by elementary analysis and by the deter- 
mination of the molecular weight. 

ELEMENTARY ANALYSIS. 

The object of elementary analysis is the determination of 
the nature and proportion of the elements contained in any 
given organic body. We can give here but a summary descrip- 
tion of the processes employed, considering only those which 
have for object the determination of carbon, hydrogen, and ni- 
trogen. These, together, with oxygen, are the more ordinary 
elements of organic combinations. 

In a substance containing carbon, hydrogen, and oxygen, 
the first two elements are determined directly in the same 
operation ; the oxygen is determined by difference. When, 
in addition to the former elements, the body contains nitrogen, 
the determination of this requires a separate operation. 

Determination of Carbon and Hydrogen. — To determine 
the proportion of carbon and hydrogen contained in 100 parts 
of any given organic substance, the carbon is converted into car- 
bon dioxide, which is collected and weighed, and the hydrogen 
into water, which is condensed and weighed. These operations 
are conducted according to the processes indicated by Liebig. 



ELEMENTARY ANALYSIS. 407 

For this end, the organic matter, previously dried with care, is 
burned with an excess of cupric oxide. The operation is exe- 
cuted in a combustion-tube of hard glass, which is wrapped with 
a spiral of metallic foil to prevent it from bending and swell- 
ing under the influence of the heat. Well-dried cupric oxide 
is introduced into the tube, then an intimate mixture of the 
substance to be analyzed with a large excess of the same oxide, 
and the remainder of the tube is filled with pure cupric oxide. 

The tube is then placed in a combustion furnace, and its 
open extremity is put in communication with (1) an U tube,,;y 
(Fig. 120), containing fragments of calcium chloride in the first 
branch, and pumice-stone impregnated with sulphuric acid in 
the second ; (2) a tube with five bulbs, A, called Liebig's potash 
bulbs, containing a concentrated solution of potassium hydrate, 
and followed by a small U tube, i, containing pumice-stone im- 
pregnated with potassium hydrate in the first branch, and frag- 
ments of potassium hydrate in the second. These difi"erent 
tubes have first been accurately weighed. When the appa- 
ratus is arranged, the combustion- tube is slowly heated, com- 
mencing at the extremity B, and gradually extending the heat 
so that each part of the tube is successively heated to redness. 
The water formed by the combustion is collected in the first 
IT tube, the carbon dioxide is absorbed by the potassium hy- 
drate in the bulbs. When the operation is terminated, the 
drawn-out point of the combustion-tube is broken, and con- 
nected by means of a caoutchouc tube with a gasometer con- 
taining oxygen. An excess of the latter gas is then passed 
through the combustion-tube, in order to drive out the traces 
of carbon dioxide and aqueous vapor which it contains at the 
end of the combustion. It is then only necessary to weigh the 
water tube and the carbon dioxide tubes. The increase in 
weight which is found indicates, on one hand, the quantity of 
water, and on the other the quantity of carbon dioxide, pro- 
duced by the combustion of the organic matter. The compo- 
sition of water and of carbon dioxide being known, it is easy 
to deduce from the weight of these two bodies the quantities 
of hydrogen and carbon contained in the analyzed substance, 
and consequently the proportion of these two elements con- 
tained in 100 parts of that substance. 

Fig. 120 represents the operation towards its close : the 
combustion-tube is in the gas-furnace, B, and communicates, 
on the right with the tubes g, h, i, destined to receive the pro- 



408 



ELEMENTS OF MODERN CHEMISTRY. 




ELEMENTARY ANALYSIS. 



409 



duct-s of the combustion, on tlic left with two hirgc U tubes, 
the first of which is filled with pumice-stone imprc\!j,iuited with 
potassium hydrate to absorb traces of carbon dioxide, the 
second with pumice-stone saturated with sulphuric acid to 
absorb moisture. Throuiih these tubes is passed the oxygen, 
at the close of the operation, to expel the last portions of carbon 
dioxide and vapor of water. 

When the substance contains carbon, hydrogen, and oxygen, 
the proportion of oxygen is the diiference between the total 
percentage of carbon and hydrogen found and 100. 




Determination of Nitrogen. — Nitrogen may be determined 
by two processes. The first consists in burning a given weight 
of the nitrogenized substance with an excess of cupric oxide. 
The carbon of the substance is converted into carbon dioxide ; 
the hydrogen is converted into water ; the nitrogen is disen- 



gaged. The 



nitrogen and carbon dioxide, are received 



in a graduated jar standing on the mercury-trough and con- 
taining potassium hydrate. The carbon dioxide is absorbed, 
the nitrogen remains. At the close of the operation, the last 
traces of nitrogen are expelled by a current of carbon dioxide. 
The volume of nitrogen is then measured, and its weight de- 
duced from its volume (Dumas). 

_ The second process (Fig. 121) consists in decomposing the 
nitrogenized organic matter with an alkali at a high tempera- 
s 35 



410 ELEMENTS OF MODERN CHEMISTRY. 

ture. By this means all of the nitrogen is converted into 
ammonia. The substance is intimately mixed with soda lime, 
that is, lime impregnated with caustic soda. The mixture is 
heated to redness in a tube of hard glass, and the ammonia is 
received in a tube with three bulbs containing dilute hydro- 
chloric acid. Ammonium chloride is formed ; when the opera- 
tion is terminated, the li(|uid containing the salt is mixed with 
a solution of platinic chloride. It is then evaporated and 
exhausted with alcohol, which leaves the platinum and ammo- 
nium double chloride, 2(NH*C1) -f- PtCl*. The latter is col- 
lected upon a tared filter, then washed and dried. From its 
weight is calculated that of the nitrogen contained in the 
organic substance (Will and Varrentrapp). 

The ammonia disengaged may also be received in 10 cubic 
centimetres of a normal solution of sulphuric acid, that is, an 
acid liquor containing a known quantity of sulphuric acid in 
a determined volume. 

The strength of this acid is determined by neutralizing 10 
c.c. of it with a dilute alkaline solution of known strength and 
noting the volume of the latter required. The same operation 
is repeated with the 10 c.c. of which the acid has been par- 
tially neutralized by the ammonia. The quantity of ammonia 
corresponds to the difference between the volumes of the alka- 
line liquid employed in these two operations, and can easily be 
calculated by simple proportion (Poligot). 

Determination of the Molecular Weight of Organic Sub- 
stances. — Elementary analysis permits the determination of 
the centesimal composition of organic substances. This is 
indispensable, but it is insufficient for the establishment of 
their atomic composition, that is, the number of atoms of car- 
bon, hydrogen, oxygen, and nitrogen which arc contained in a 
single molecule of a given organic compound. But if the 
weight of the molecule be known (hydrogen being taken as 
unity), it is easy to deduce the atomic composition from the 
figures given by elementary analysis, as will be seen by the 
following example. By elementary analysis it is found that 
100 parts of acetic acid contain 

Carbon 40. 

Hydrogen 6.67 

Oxygen 53..S.3 

f 00 .7)0 

On the other hand, methods which will be described have 



ELEMENTARY ANALYSIS. 411 

shown that the niok^cular wciulit of acetic acid is GO ; that is to 
say, the total weight of the atoms of carbon, hydrogen, and 
oxygen contained in a molecule oi' acetic acid, is GO. 
Hence by the following proportions : 

If 100 parts acetic acid contain 40 of carbon, 60 parts contain jc. 
" " " 6.67 of hydrogen, " " y, 

*' " " 53.33 of oxygen " " z. 

From which, x = 24,- y = 4; z == 32. 
Hence 24 represents the weight of the atoms of C contained in a molecule 

of acetic acid. 
4 represents the weight of the atoms of H contained in a molecule of acetic 

acid. 
32 represents the weight of the atoms of contained in a molecule of acetic 
acid. 

By dividing these numbers by the weights of the respective 
atoms, the number of atoms of C, H, and contained in a 
molecule of acetic acid is readily determined. 

24 -i- 12 = 2 atoms of carbon. 
4 -h 1 = 4 " hydrogen. 

32 -!- 16 = 2 " oxygen. 

Hence the formula of acetic acid is C-H*0^ 

After the analysis of an organic substance has been made, it 
is only necessary to determine its molecular weight in order to 
establish its atomic composition. Several processes are em- 
ployed for this determination, of which the most sure is the 
determination of the vapor density. 

We know that if one atom of hydrogen occupy one volume, 
the molecules of organic substances occupy two volumes. To 
find the weights of these molecules it is then sufficient to deter- 
mine their vapor densities compared to hydrogen ; that is, to 
find the weight of one volume of their vapors, that of one 
volume of H being taken as unity. The number found mul- 
tiplied by 2 gives the weight of two volumes, that is, the weight 
of the molecule. 

Hence a simple determination of the vapor density is suf- 
ficient for the establishment of the molecular weight. Ordi- 
narily these vapor densities are given as compared with air 
taken as unity. To bring them to the hydrogen scale it is 
then only necessary to multiply them by 14.44, which is the 
exact relation of the density of air to that of hydrogen. Thus 
the vapor density of acetic acid, determined at 295°, has been 
found equal to 2.083 (Cahours). This number multiplied by 
14.44 gives for the density compared to hydrogen 30.08. The 



412 ELEMENTS OP MODERN CHEMISTRY. 

latter number expresses the weight of one volume of acetic 
acid vapor, the weight of one volume of hydrogen being con- 
sidered as 1. The weight of two volumes of this vapor, that 
is, the weight of the molecule, will then be 2 X 30.08 = 
60.16, a number very nearly approaching 60, the theoretical 
molecular weight. 

The method just described can only be applied to substances 
which can be volatilized without decomposition. For other 
bodies another method must be adopted. The latter consists 
in forming with the organic body definite combinations, the 
atomic composition of which may be known. We will again 
consider acetic acid. Salts may be formed with this acid, and 
we know that these salts contain one atom of metal. We may 
then analyze silver acetate. 100 parts of that salt contain 
64.67 parts of silver. This fact being known, it is easy to deter- 
mine the molecular weight of silver acetate. Since the latter 
contains one atom of silver, we can conclude, if 64.67 parts of 
silver are contained in 100 parts of silver acetate, 108 parts 
of silver, that is, one atom, are contained in x parts of silver 
acetate ; whence x = 167. This number represents the molec- 
ular weight of silver acetate. That of acetic acid may be de- 
duced by substituting the atomic weight of hydrogen for that 
of silver, which gives for the molecular weight of acetic acid 60. 

Analogous operations and reasoning permit the determina- 
tion of the molecular weights of bodies playing the part of 
bases. They are combined with an acid, the molecular weight 
of which is known, and the composition of the combination 
furnishes the data for the calculation of the molecular weight 
of the base. This method can be applied in a large number 
of analogous cases, and presents a great generality. 

ISOMERISM, METAMERISM, POLYMERISM. 

Elementary analysis demonstrates that many bodies which 
differ in their physical and chemical proparties, possess exactly 
the same centesimal composition. Such bodies are said to 
be uomeric. Two kinds of isomerism exist. Sometimes the 
isomeric bodies contain the same number of similar atoms in 
molecules of the same size, and differ only by the arrange- 
ment of these atoms ; sometimes they contain similar atoms 
united in the same proportion, but not in the same number, in 
molecules of unequal magnitude. 



ISOMERISM, METAMERISM, POLYMERISM. 413 

In both cases the ccntesiiiial eoiiiposition is the same, I'ur it 
depends only on the rehitive number of the atoms. 

The first kind of isomerism constitutes metamerism ; tlie 
second, polj/merism. Acetic acid and methyl formate are an 
example of two metameric bodies. Each contains 2 atoms of 
carbon, 4 of hydrogen, and 2 of oxygen ; their molecules are 
equal in size, but different in atomic structure. The latter fact 
may be expressed by the following formulae : 

Cm^O.OH acetic acid 
CIPO.OCH methyl formate 

The first expresses that acetic acid contains a group of atoms, 
C"'H''0, acetyl, which is united with hydroxyl, OH ; the second, 
that methyl formate contains a group, CHO, formyl, which is 
united with oxymethyl, CH'^O. The difference in the atomic 
arrangement becomes evident, if the preceding formula3 be 
developed in the graphic manner. 

0-H 0-CW 

C=0 C=0 

I I 

CH^ H 

Acetic acid. Methyl formate. 

By adopting the theory of atomicity, chemists have been 
enabled to discover the atomic structure of a great number of 
combinations, as we have seen in the case of acetic acid and 
methyl formate. Such considerations are of great importance 
for the interpretation of isomerism, and we will have frequent 
occasion to refer to the subject in the course of this work. 

Acetic acid and glucose or grape-sugar present an example 
of 2)ol?/merism. Both contain the atoms of carbon, hydrogen, 
and oxygen, united together in the same proportions, but the 
molecule of the second contains three times as many of each 
as that of the first. 

C2H'^02 acetic acid. 
3 X C2H*02 = C6H1206 glucose. 

Among the more important and better known cases of po- 
lymerism, may be mentioned the numerous hydrocarbons which 
present the centesimal composition of ethylene or defiant gas, 
and which differ from it by the regularly increasing number of 
their atoms of carbon and hydrogen. These bodies form the 
following homologous series : 

35^ 



414 ELEMENTS OP MODERN CHEMISTRY. 



cm* 


ethylene. 


C'1I« 


])r()j)ylene. 


cms 


butylene. 


C51110 


ainylenc. 


C6H12 


hexylene. 


C^UH 


beptyleue. 


C8Hifl 


octylene, etc. 



It will be seen that butylene contains twice as many carbon 
and hydrogen atoms as ethylene, hexylene contains three times 
as many, etc. 

FUNCTIONS OF ORGANIC COMPOUNDS. 

In the study of mineral chemistry it has been seen that 
bodies present great differences in properties, according to their 
composition. Some are simple and apt to enter into combina- 
tion ; others are compound and indifferent ; the first are more 
or less energetic in their affinities, the others saturated and 
satisfied. In one case, we have examined either more or less 
powerful acids or bases, some of which are hydrated, as potassa 
and soda, others anhydrous, as the oxides of lead and silver. 
In the other case, we have studied the salts resulting from the 
union of the former bodies. 

In organic chemistry we again encounter various kinds of 
bodies which have different functions, according to their com- 
position. 

It may be said, in a general manner, that the properties of 
compound bodies depend upon the nature of the atoms and 
their arrangement in the molecule. In treating of isomerism, 
the influence of the latter condition has been indicated ; that 
of the former is still more powerful. 

Water and potassium hydrate are both constituted, and in 
an analogous manner, of three elementary atoms. Each con- 
tains one atom of oxygen united to two monatomic atoms. 

HOH KOH 

Water. Potassiiini hydrate. 

But what a difference in their properties ! But may not 
this be expected when it is considered that one contains the 
energetic metal potassium, in the place occupied in the other 
by the light gas hydrogen ? Is the difference between potassa 
and water greater than that between potassium and hydrogen ? 



AION ATOMIC COMPOUNDS. 415 

And if for the two atoms of hydrogen we substitute two atoms 
of chloriue, is it not to be expected that hypochlorous oxide 

Cl-O-Cl 

the molecule of which is similar in structure to that of water, 
shall differ from the latter in its properties as much as chlo- 
rine differs from hydrogen ? It is thus that the nature of the 
elements contained in compound bodies is the dominant condi- 
tion in the manifestation of their properties. 

The following considerations are of a nature to demonstrate 
the truth of this proposition inasmuch as concerns organic 
compounds : 

MONATOMIC COMPOUNDS. 

Saturated Hydrocarbons. — Tho hydrocarbons belonging 
to the series of marsh gas are all saturated. Consider, for 
example, C'^tP ; all of the atomicities of two atoms of carbon 
are satisfied by the union of tha latter tog3ther and with six 
atoms of hydrogen. 

H H 

H-C-C-H 

I I 
H H 

Ethana, or ethyl hydride. 

It is the same with all of its homologues ; the hydrides of 
propyl, butyl, amyl, etc., are all saturated hydrocarhons^ as will 
be seen by developing the formula of any one of them, pentane, 
for example : 

HHH H H 

I I I I I 

H-C-C-C-C-C-H 

I I I I I 

H H H H H 

Pentane, or amyl hydride. 

All of these bodies are incapable of fixing other elements 
by direct additioR, but they may be modified by suhstitution, 
that is, one or several of their atoms of hydrogen may be 
replaced by other elements. 

Monatomic Chlorides, Bromides, and Iodides. — By the 
reaction of bromine upon any of the hydrocarbons, we may 



416 ELEMENTS OF MODERN CHEMISTRY. 

obtain compounds containing an atom of bromine in the place 
of an atom of hydrogen. 

eiP -j- Br^ = CH^Br + IIBr 

Ethane. Ethyl bromide. 

A saturated and indifferent hydrocarbon is thus converted 
into a bromide. 

The corresponding chloride and iodide exist, possessing the 
same constitution as the primitive hydrocarbon, and forming 
with it the following series : 

C2H6 ethane. 
C2H5C1 ethyl chloride. 
C'^ll^Br ethyl bromide. 
Cni^l ethyl iodide. 

To the other hydrocarbons correspond chlorides, bromides, 
and iodides analogous to the preceding. Thus, the following 
groups are known : 

CII* methane. C5H12 pcntane. 

CH3CI methyl chloride. C^RHCl amyl chloride. 

CIl-^Br methyl bromide. C^H^Br omyl bromide. 

CIl^I methyl iodide. CHV^l amyl iodide. 

All of these bodies may be made to undergo the most varied 
transformations. The}^ may be attacked by a number of re- 
agents, to which they present a hold, as it were, since the chlo- 
rine, bromine, and iodine which they contain are gifted with 
powerful affinities. 

The residues resulting from the subtraction of the chlorine, 
bromine, or iodine then enter into other combinations. It will 
be remarked that these residues represent the saturated hydro- 
carbons from which one atom of hydrogen has been removed. 

CH^ = CH^^Br — Br, or CH* — H 
C-'H^ r= C-IPBr — Br, or C^H« — H 
C^H" = C^H^^Br — Br, or C^IP^ — H 

The atoms of carbon contained in these residues, CH'', C^IP, 
and C^H^\ are no longer entirely saturated, since CI, Br, I, or 
H has been removed, elements which saturated one atomicity. 
Therefore, these residues are capable of entering other com- 
binations, but as they possess only one free atomicity, they can 
only saturate one when they combine. This is expressed by 
saying that they play the part of monntnmic radicals. The 
chlorides, bromides, and iodides from which they are derived 
are themselves monatomic. 



MONATOMIC COMPOUNDS. 417 

Alcohols. — The neutral organic hydrates corresponding to 
the preceding chlorides, bromides, and iodides, are called 
alcohols. 

If ethyl iodide be heated for a sufficiently long time with 
potassium hydrate, potassium iodide will be formed, and the 
alkaline liquid will contain alcohol which may be separated. 

This body is ethyl hydrate and is formed according to the 
following reaction : 

en^I -f KOH = KI 4- C^H^.OH 

Ethyl iodide. Ethyl hydrate. 

It is formed, as is seen, by double decomposition. The 
potassium having removed the iodine from the ethyl iodide, 
the monatomic residue C-H^ combines with the monatomic 
residue OH. Alcohol is then the hydrate which corresponds 
to the iodide, C^H^I, and to the hydrocarbon, C'^H^. Analo- 
gous hydrates correspond to the other hydrocarbons of tlie 
same series ; they constitute the series of monatomic alcohols, 
and may be defined as derived from the saturated hydrocarbons 
by the substitution of the group hydroxyl for one atom of 
hydrogen. The alcohols now known are numerous ; the follow- 
ing are some of them : 

CH3.0H methj'l hydrate, or methylic alcohol, 
- C-'IP.OH ethyl hydrate, or ethylic alcohol. 
C-^H'.GH propyl hj-drate, or propylic alcohol. 
C*H9.0H butyl hydrate, or butylic alcohol. 
C^H^i.OH amy] hydrate, or araylic alcohol. 
C^H^^.OH hexyl hydrate, or hexylic alcohol. 
C^H15.0H heptyl hydrate, or heptylic alcohol. 
C^H^^.OH octyl hydrate, or octylic alcohol. 

Each member of this series differs from that which follows 
by — CH^ All are allied by analogous properties. These two 
conditions characterize homologous bodies. The alcohols of 
which the general formula is CH-^+^OH, form one of the most 
important series of homologues. 

If one of these alcohols be heated with hydrochloric, hydro- 
bromic, or hydriodic acid, water will be formed and the alcohol 
will be converted into a monatomic chloride, bromide, or iodide. 
In this reaction the hydroxyl, OH, is replaced by chlorine, 
bromine, or iodine. 

C^H^OH + HCl = WO + C^H^Cl 

Ethyl hydrate. Ethyl chloride. 

The bodies thus formed are the monatomic chlorides, bro- 



418 ELEMENTS OF MODERN CHEMISTRY. 

mides, or iodides before considered. These experiments expose 
the rekitions which exist between the hitter compounds and the 
corresponding hydrates, which are tlie alcohols. 

Monobasic Acids. — Acetic acid, which exists in vinegar, is 
a derivative of alcohol, of which it is one of the products of 
oxidation. It is formed under many conditions, one of which 
is the oxidation of alcohol vapor on contact with platinum 
black and the air. 

Cm\Oll -f 0' = C^IPO.OH f H^O 

Alcohol. Acetic acid. 

In this reaction an atom of oxygen removes two atoms of 
hydrogen to form water, and the place of these two atoms of 
hydrogen is filled by another atom of oxygen. The group 
ethyl, C'^H^, thus becomes the group acetyl, C'H'*0, and if 
alcohol be the hydrate of ethyl, acetic acid is the hydrate of 
acetyl. We can account for this reaction by developing the 
formulae of alcohol and acetic acid according to the principles 
before explained. 

H H HO 

H-C-C-OH + 0^ = H-C-C-OH + IPO 
I I I 

H H H 

Alcohol. Acetic acid. 

In alcohol, the second carbon atom is combined with two 
atoms of hydrogen and with one group hydroxyl, while in 
acetic acid it is combined with an atom'of oxygen and a group 
hydroxyl. 

Acetic acid contains two atoms of carbon united together, 
and combined, the one with H\ the second with and OH. 
It is thus formed of a group CH'^ united to a group CO-OH 
= CO'H. There exist many other acids analogous to acetic 
acid, and derived, like it, by oxidation of the monatomic alco- 
hols of the series C"H''^"^^OH. All of these acids contain 
a hydrocarbon group analogous to methyl, combined with the 
group CO'H = CO-OH. The hydrogen of the latter group 
can be readily replaced by an equivalent quantity of metal. 
This hydrogen is said to be strongly basic, and all of the organic 
acids which contain a single group, CO'H, united to a hydro- 
carbon group, are mouohasic like acetic acid. The homologues 
of the latter form the following- series: 



MONATOMIC COMPOUNDS. 419 

C 112 02 = II -C02II formic acid. 
C2 114 02 = C 113 _C021I acetic acid. 
C'i 116 02 := C2H» -C021I propionic acid. 
C* Il« 02 = C311T _C02H butyric acid. 
Co RIOO' = C^IP -C021I valeric acid. 
Oe II1202 = C^llii-CO'^lI caproicacid. 
C7 111102 = C6I113-C02II tt'iianthic acid. 
C8 IIi«02 = Cnii5-C02II caprylic acid. 
C9 Ui802== C8H"-C02H pelargonic acid. 
C10H20O2 _, C9H19-C02H capric acid, etc. 

The first series of f()rnmh"e indicates simply the nature and 
number of atoms contained in the acids of the series C"H-"0'. 
They are empirical formulae. The second series gives certain 
indications upon the relations existing between these atoms. 
They are rational formulas, and when developed so as to ex- 
press the relations between all of the atoms, they become 
constitutional formulae. 

Compound Ethers. — The compound ethers are combina- 
tions which represent acids of which the hydrogen has been 
replaced by an alcoholic group. 

If one of the alcohols of the preceding series, ordinary alco- 
hol, for example, be heated for a long time with acetic acid, 
water will be formed, and a volatile, neutral liquid possessing an 
agreeable odor may be separated from the product ; this sub- 
stance is ethyl acetate, or acetic ether. It is formed according 
to the following reaction : 

en^OH + c^H^^o.OH =. c'wo^C'wo) -f wo 

Alcohol. Acetic acid. Eth^'l acetate. 

On comparing this compound with alcohol, we find that it 
is formed by substitution of the group C'H'^O, the existence of 
which is admitted in acetic acid, and which is called acetyl, 
for one atom of hydrogen in alcohol ; and this atom of hydro- 
gen which is replaceable by acetyl is that which is united to the 
oxygen in alcohol, — that Avhich forms a part of the hydroxyl 
group. The other atoms of hj^drogen, those which constitute 
part of the group C'H'^, cannot be replaced by acetyl. 

All of the acids can form with alcohol, and indeed with all 
of the alcohols, compounds analogous to ethyl acetate, and 
these combinations are called compound ethers. The property 
possessed by the alcohols of etherifying acids is general and 
characteristic of this class of compounds. Alcohols which 
require for etherification but a single molecule of an acid anal- 



420 ELEMENTS OF MODERN CHEMISTRY. 

ogous to acetic acid are called monatomic. Many exist whicli 
are not included in the preceding series. 

Aldehydes. — Acetic acid is not the only product of the 
oxidation of alcohol. There is another compound interme- 
diate between these two ; it results from the action of a single 
atom of oxygen upon the molecule of alcohol, which thus loses 
two atoms of hydrogen without other change. The new com- 
pound is aldehyde. 

Alcohol. Aldehyde. 

It is a very volatile liquid having a great tendency to become 
oxidized and converted into acetic acid. It forms crystalline 
combinations with the alkaline acid-sulphites. To the other 
alcohols of the series C"H*^"+'^0, and other acids of the series 
(-jn jj2nQ2^ correspond compounds analogous to aldehyde by their 
composition and by their properties. They form the following 
series : 

C^H^O aldehyde or acetaldehyde. 

C^H^O propionic aldehyde. 

C^HSQ butyric aldehyde. 

CoHiOQ valeric aldehyde, etc. 

Acetones. — When calcium acetate is submitted to dry distil- 
lation a neutral, volatile liquid is obtained, having a peculiar 
aromatic odor, and known by the name acetone. 

Calcium acetate. Acetone. Calcium carbonate. 

To the other acids of the acetic acid series correspond bodies 
analogous to acetone, and forming with it a homologous series. 
These acetones are related by properties and composition to the 
aldehydes. Like the latter, they form crystalline combinations 
with the alkaline acid-sulphites. It may be considered that 
while aldehyde is the hydride of acetyl, acetone is the methyl- 
ide of acetyl, and that in general the acetones are derived by 
the substitution of an alcoholic group, analogous to methyl, for 
an atom of hydrogen in the aldehydes considered as hydrides. 

CH^-CO-H CH^-CO-CH^ 

Aldehyde (acetyl hydride). Acetone (acetyl methylide). 

Hence, acetone contains two methyl groups united to a group, 
CO (carbonyl). Its mode of formation justifies this conclusion, 



MONATOMIC COMPOUNDS. 421 

as shown in the following- cquution, in which the constitutional 
formula of acetic acid is employed : 

CH^'-COO^^^ = Ca"CO^ + Cff-CO-CH^ 

Calcium acetate. Calcium carbonate. Acetone. 

Chlorides of Acid Radicals. — In the preceding compounds 
we have admitted the existence of a i^roup, C'^H^O^: CH^-CO, 
existing in combination with OH in acetic acid, C-'H^O.OH, 
with hydrogen in aldehyde, C-H^O.H, and with methyl in ace- 
tone, C'-^H'^O.CH^ A compound is known in which this same 
group is united with chlorine. Acetyl chloride, C^H'O.Cl, is 
a monatomic chloride, like ethyl chloride, C'"1PC1, from which 
it is distinguished by the strongly electro-negative nature of 
its radical. 

If acetyl chloride be poured into water, it disappears in a 
short time with development of heat and the formation of acetic 
and hydrochloric acids. 

C'H^O.Cl + IPO = C'ffO.OH + HCl 

Acetyl chloride. Acetic acid. 

To acetyl chloride correspond other chlorides which contain 
radicals, of acids analogous to acetic acid. When they are 
treated with water they yield hydrochloric acid and the acids 
corresponding to their radicals. 

C^ffO.Cl C^H^O.OH 

Propionyl chloride. Propionic acid. 

C^H'O.Cl C^H^O.OH 

Butyryl chloride. Butyric acid. 

C'H^O.Cl C^H^O.OH 

Benzoyl chloride. Benzoic acid. 

Amides. — If acetyl chloride be treated with ammonia, am- 
monium chloride will be formed, together with a solid, neutral, 
nitrogenized body called acetamide. 

effO.Cl -f- 2NH3 =: NH*C1 4- C'H^O.NH^ 

Acetyl chloride. Acetamide. 

There are many other compounds similar to acetamide, and 
known by the name amides. They are formed by the action 
of ammonia upon organic chlorides analogous to acetyl chloride. 
They are also formed by the action of heat upon the ammo- 
niacal salts of the monobasic acids. The latter compounds 
then lose one molecule of water, and are converted into amides. 
C^H^O.ONH^ = C^H^O.NH^ -f H^O 

Ammonium valerate. Valeramide. 

36 



422 ELEMENTS OF MODERN CHEMISTRY. 

Acetamide may be regarded as ammonia in which an atom 
of hydrogen has been rcphiced by the radical acet}^. 

( H ( C-'IPO ( C^H»0 

N H N .' H N -! H 

(h (h (H 

Ammonia. Acetumide. Valeraiiiide. 

Compound Ammonias, or Amines. — If ethyl iodide be 
heated with aumionia, one of the products of the reaction will 
be the hydriodide of a base derived from ammonia by the sub- 
stitution of an ethyl group for an atom of hydrogen. 

Cm'l + NH^ = (C-'IP)NIP.HI 

Ethyl iodide. Etliylamiiie hydriodide. 

In this reaction, other ethylated bases are formed, independ- 
ently of ethylamine, among which must be mentioned diethyl- 
amine and triethylamine. All present the most striking anal- 
ogy to ammonia. They may be regarded as ammonia in which 
one, two, or three atoms of hydrogen have been replaced by 
one, two, or three ethyl groups. 





cm') 

H ^N 
Hi 


cm' ) 


C^IP) 


H^ 


H \ 


eip \ 


Ammonia. 


Ethylamine. 


Diethylamine. 


Triethylamine. 



The other alcoholic groups, C"H''"^\ can in the same man- 
ner replace one or more atoms of h^^drogen in ammonia. The 
results are bases having constitutions analogous to those of the 
ethyl bases. They are called (uniueSj or compound ammonias. 

It is necessary that the signification of the formulae above 
given and those that are to follow shall be clearly understood. 
They are examples of typical notation, and indicate the rela- 
tions of the compounds with the type ammonia. 

N'" ] H 
(H 
The brace joining the three hydrogen atoms signifies that 
the whole three are united to a single atom of triatomic nitro- 
gen, with which each exchanges one atomicity; this may bo 
expressed by writing the formula for ammonia thus : 

N'VH 



MONATOMIC COMPOUNDS. 423 

Wliat, then, takes place when one or niore atoms of hydro- 
gen are rephiced by a uroup like ethyl ? The latter exchanges 
one atomicity with the nitrogen atom, ])recisely as the hydro- 
gen atom did, and combines with the nitrogen by one of the 
atoms of carbon of the group ethyl, CH' -CH^, which requires 
the satisfaction of one atomicity. 

This is clearly expressed in the following graphic formuUx) : 
H H ^ 

N-CH^-CH^ N-Cir^-CIP 

H CH^-CH^ 

Ethylamine. Diotlijiamine. 

However, such formula3 would be too cumbrous for ordinary 
use, and our formula? must be more condensed. 

^H ^H 

Etliylamine. Diethylamine. Trietliylaraine. 

Phosphines. — Arsines. — Stibines. — There exist several se- 
ries of combinations belonging to the same type as the com- 
pound ammonias, but in which the nitrogen is replaced by 
phosphorus, arsenic, or antimony. These compounds are de- 
rived from the hydrogen compounds of phosphorus, arsenic, 
and antimony by the substitution of one or more alcoholic 
groups for one or more atoms of hydrogen. 



RVF H V P C^H^ [ P C^H^ }■ P 

H \ H ) H ) cm' ) 

Hydrogen phosphide. Ethvlphosphine. Diethyljihosphiiie. Triethyli)hospIiine. 

H) CW) CHn CHM 

H Us H C As CHn As CH=' [ As 

H j H ^ CI 3 CH^^ ) 

Hydrogen arsenide. Methylarsiiie. Dimetliylarsine Trimethyhirsine. 

H [ sb — — cm' [ sb 

H ) C'H^ ) 

Hydrogen antinionide. Triethylstibine. 

Organo-metallic Compounds. — Ethyl and its congeneric 
compounds, methyl, amyl, etc., can enter into combination not 
only with nitrogen, phosphorus, arsenic, etc., of which they 
saturate one or more atomicities, but with a large number of 



424 ELEMENTS OP MODERN CHEMISTRY. 



metals. Thus, zinc, which is diatomic, can combine with two 
ethyl groups to form zinc ethyl. 

Mercury, also diatomic, can unite with one or two ethyl or 
methyl groups, etc. In the second case, the new combination 
is saturated; in the first, it is monatomic, (Hg"C-'H^j', and re- 
quires for saturation an atom of a monatomic element, or a 
monatomic group, iodine, for example. 

Hg j ^.jj5 Hg I J 

Mercur-ethyl. Mercnr-niunethyl iodide. 

Bismuth, which is triatomic, can fix three ethyl groups. 
Bi'" \ C'H^ 

( en^ 

Bismuth-ethyl. 

Stanno-tetrethyl is formed by the union of four ethyl groups 
with one atom of tetratomic tin. 

If the four atomicities of tin be not all satisfied, non-satu- 
rated compounds may be formed. 



-{ 



niSs -Sn-.' eH^ or -Sn'^'^CfH^ 



Stanno-diethyl. Staniio-triethyl. 

Stanno-diethyl is known in the free state, but stanno-triethyl 
doubles its molecule as soon as it is set at liberty, combining 
with itself, as it can combine with iodine. 

ISn'^C^H-^)^ (eH^/Sn'^'-Sn'^(C^ff/ ^ Sn^eH^j^. 

Stanno-triethyl iodide. " Sesquistannetliyl. 

Non-saturated compounds are apt to combine with other 
elements or radicals. Stanno-tetrethyl, which is saturated, does 
not possess this faculty. 

Tlie bodies just mentioned belong to the class of organo- 
metallic compounds. Their study is of great importance in 
the history of the atomicity of the metals, that is, their power 
of saturation. The theoretical considerations concerning them 
have been discussed by Frankland, Baeyer, and Cahours. 



MONATOMIC RADICALS. 



425 



Monatomic Radicals. — From the preceding summary may 
be understood tlie position occupied in organic chemistry by 
certain groups containing carbon, groups that are distinguished 
as monatomic because they can manifest but a single atomicity. 
Only a single monatomic atom or group is wanting that all of 
the carbon atoms contained in these groups may be entirely 
saturated. These groups of atoms or radicals cannot exist in 
the state of liberty, but they can pass from one compound to 
another, replacing a single atom of hydrogen or other mon- 
atomic element, and consequently playing the part of that ele- 
ment in the new combination. This is expressed by saying 
that these groups act as monatomic radicals. 

To indicate the constitution of the combinations containing 
such groups, and especially the metamorphoses that they may 
undergo by exchanging these radicals by double decomposition, 
it is convenient to distinguish the latter by unique expressions, 
occupying a place in the formula distinct from that of the 
other elements. The composition of all of the bodies which 
have just been reviewed may be represented by very simple 
formulae, by comparing them to hydrogen compounds, such as 
free hydrogen, or hydrochloric acid, water, and ammonia. The 
notation then assumes a typical form, exceedingly clear for the 
interpretation of the majority of reactions. 

The following are the typical formulae for the combinations 
that have been considered : 

H 



TiPE HH. 
Ethyl chloride. 

(eH-^O)Cl 

Acetyl chloride. 

(C'ffO)H 

Aldehyde. 

(C^H^OjCCH^) 



Type 



n}o. 



Ethyl hydrate. 
Ethyl oxide. 

(C^H'O) j 

Acetic acid. 

Etiiyl acetate. 
36* 



Type H ^N. 

H fN 

Ethylamine. 

Diethylamine. 

Tiiethvlamine. 

CCm'^O)-) 
H fN 

Acetaniide. 



426 ELEMENTS OF MODERN CHEMISTRY. 



POLYATOMIC COMPOUNDS. 

If chlorine and defiant gas, or ethylene, be mixed in equal 
volumes, both gases disappear and are converted into an oily 
substance, which was formerly called Dutch liquid. This body 
results from the combination of a molecule of ethylene with a 
molecule (two atoms) of chlorine. It is ethylene chloride. 

e^H* -f cr^ = c'H^cp 

Ethylene. Etliyleiie chloride. 

If the constitution of ethylene gas, C"H*, be compared with 
that of the saturated hydrocarbon ethane, C'^H^, which like the 
former contains two atoms of carbon, it will be noticed that it 
contains two atouis of hydrogen less. 

C'H« — H^ = C'H* 

In ethylene the six atomicities of the pair of carbon atoms 
are not saturated. Hence that gas can absorb directly two 
atoms of chlorine, bromine, or iodine to form a saturated com- 
pound. 

HH H H HH 

II II II 

H-C-C-H -C-C- Cl-C-C-Cl 

II 11 II 

HH HH HH 

Ethane. Ethylene. Ethylene chloride. 

It is a diatomic radical, and it can exist in the free state 
because until other atoms are presented to satisfy the atom- 
icities of the two atoms of carbon, those two atoms are bound 
together by a double affinity. Thus, WC=CR\ One of 
these bonds is loosed when the ethylene manifests its affinities 
and enters directly into combination, because the affinity of 
carbon for chlorine or such an element is greater than its 
affinity for carbon Ethylene is the first of a numerous class. 
The following bodies form with it the homologous series CH''" : 

C2H* ethylene. 

C^fl^ propylene. 

C*I18 butylcne. 

C^II^o aniylene. 

€61112 hc.xylene. 

CUP* heptylenc. 

C8I116 octylene. 

C^IP^ nonvlenc. 
CiOH-iO dccylene, etc. 



POLYATOMIC COMPOUNDS. 427 

All of these bodies are able to tix directly two atoms of 
chlorine or bromine. When they enter into combination, they 
take the place of two atoms of hydrogen. They can pass by 
double decomposition from one compound to another, and their 
combinations may undergo various metamorphoses analogous 
to those already indicated. 

Diatomic Alcohols or Glycols. — The glycols are compounds 
in which the two atomicities of the diatomic radicals are saturated 
by two hydro xyl groups. The two atoms of bromine in ethy- 
lene bromide, C'H^Br', may bo replaced by two hydroxyl groups 
(Oil), and the resulting combination is ethylene dihydrate. 

The two atoms of hydrogen united to the oxygen in the 
hydroxyl groups in glycol may both be replaced by acid radi- 
cals analogous to acetyl, just as the single atom of hydrogen in 
the single hydroxyl group of a monatomic alcohol may be 
replaced by an acid radical. This is characteristic of a diatomic 
alcohol. 

To ethylene dihydrate, or ordinary glycol, correspond the 
hydrates of the other hydrocarbons homologous with ethylene. 
The following glycols are known : 

C^H^ { OH S^^"^^' 

CnV I ^{J propylglycol. 

C*H8 J ^^ butylgljcol. 
C5H10 I ^{J amylglycol. 
C6H12 I ^JJ hexylglycol, etc. 

Around each of these bodies are grouped a great number of 
derivatives, among which we can only consider the ethers, acids, 
and compound ammonias. 

Ethers of the Glycols. — The ethers of the glycols result 
from the substitution of alcoholic or acid radicals for the hydro- 
gen of the groups OH. One or both of these hydrogens may 
be thus replaced, and the following examples will illustrate the 
constitution of the compounds so formed : 

^ ^ I OH ^ ^ 1 O.C2H5 '^ ^^ I OH ^ ^N O.C^H^^O 

Monethylic glj'col. Dietlijiic glycol. Glycol mona;etate. Glycol diacetate. 



428 ELEMENTS OF MODERN CHEMISTRY. 

Diatomic and Dibasic Acids. — Diatomic acids result from 
the oxidation of the glycols. Their formation and constitu- 
tion may be understood by developing the formulae of the 
hydrocarbons which constitute the radicals of these glycols. 
Ordinary glycol may yield two acids by oxidation, the first 
resulting from the substitution of an atom of oxygen for two 
atoms of hydrogen, the second from the substitution of two 
atoms of oxygen for four atoms of hydrogen. The following 
formulas express the constitution and derivation of these com- 
pounds : 

CH^ Cff^Br CmOH CHIOH CO.OH 

CW CH^Br CHIOH CO.OH CO.OH 

Ethylene. Ethylene bromide. Glycol. GlycoUic acid. Oxalic acid. 

Glycollic and oxalic acids, which are produced by the oxida- 
tion of glycol, are both diatomic because they are both derived 
from a diatomic alcohol ; but the first is monobasic because it 
contains but a single atom of hydrogen that can be replaced by 
a metal. The second is dibasic, for it contains two atoms of 
hydrogen that are replaceable by an equivalent quantity of metal. 
This basic hydrogen is that which forms part of the group 
CO'^H. Oxalic acid is composed simply of two groups -CO'^H ; 
it is. dibasic. Glycollic acid contains but one, and it is conse- 
quently monobasic. The hydrogen united to the oxygen in 
the group -CH'^OH is called alcoholic hydrogen ; it may be 
replaced by an acid radical, but it cannot be easily replaced by 
a metal. All bodies containing a group CH'^OH are alcohols, 
and all bodies containing a group CO.OH are acids. The 
alcohols and acids are thus defined by their constitution. Gly- 
collic acid is at the same time an alcohol and an acid, for it 
contains both a group CH'^.OH and a group CO.OH. 

There exists a series of acids homologous with glycollic acid, 
and another series homologous with oxalic acid. Both series 
appertain to the superior diatomic alcohols. 

Diatomic Ammonias or Diamines. — Compounds exist 
which hold the same relation to the diatomic alcohols as ethyl- 
amine and its homologues to the monatomic alcohols. Such 
a compound is ethylene-diamine. Its relations with ethylene 
chloride and glycol are expressed by the following formulae : 

eH'<^} C'H'<SS '^'H'<NH^ 

Ethylene chloride. Glycol. Ethylene-diamine. 



CYANOGEN. 429 

Alcohols of Higher Atomicity. — There arc alcohols of 
higher atoniitity; ulycerin, for example, is a triatomic alco- 
hol. It contains a radical, CMl", which is triatomic since it is 
derived from the saturated hydrocarbon C"'IP, by the subtrac- 
tion of three atoms of hydrogen. Erythrite is a tctratomic 
alcohol ; it contains i\\Q tetratoiiiic radical C'H« = C^IF® — H*. 
Lastly, the sweet, sugar-like substance derived from manna 
and known as mannite is a hexatomic alcohol. There are 
numerous similar substances which are alcohols of higher 
atomicity. The following formulae express the composition 
and the functions of theso j^olj/afomic alcohols: 

OH 



roH 




C^H^'" -^ OH C^H«- J. y^lj C«H«-(OH)« 

(oh 

Glycerin. Erythrite. Maunite. 

Around these bodies are grouped the numerous correspond- 
ing derivatives, ethers, acids, etc. 

It w ill be seen by the preceding considerations that the neu- 
tral h^'drates, called alcohols, are highly important in them- 
selves and on account of the derivatives which attach to them. 
Hence the elements of a natural classification of organic com- 
pounds are deduced. 



'&" 



COMPOUNDS OF CYANOGEN. 

Gay-Lussac gave the name cyanogen to the radical of prussic 
or hydrocyanic acid, which was discovered by Scheele in 1782. 
This radical is composed of one atom of carbon and one atom of 
nitrogen. In hydrocyanic acid it is united with hydrogen ; in 
the cyanides it is combined with the metals. 

H(CNy K(CNy . Hg"(CN)^ 

Hydrocyanic acid. Potassium cyanide. Mercury cyanide. 

The preceding compounds may be compared with the corre- 
sponding chlorides : 

HCl KCl HgCF 

Hydrochloric acid. Potassium chloride. Mercuric chloride. 

It is somewhat remarkable that potassium cyanide is iso- 
morphous with potassium chloride. 

In the preceding compounds, cyanogen, which is composed of 
an atom of carbon and an atom of nitrogen, plays a part anal- 
ogous to that of chlorine. It is a monatomic radical ; nitrogen, 



430 ELEMENTS OF MODERN CHEMISTRY. 

wliic'h is triatomic, can saturate only three of the four atomici- 
ties whicli reside in an atom of carbon. Hence there remains 
one free atomicity, and cyanogen can act as a monatomic radi- 
cal, -CeN. 

CYANOGEN. 

(CN)2 = Cy-^ 

Preparation. — Mercury cyanide is heated in a small retort 
fitted with a delivery-tube. The mercury volatilizes, and a gas 
is disenga<;ed which may be collected over mercury. There 
remains in the retort a solid brown mass which possesses the 
same composition as cyanogen, and is known i\s, paracyatLogeii. 

Hg(CN)^ = (CNy^ + Hg. 

Composition and Properties. — Cyanogen is a colorless gas, 
possessing a strong odor of bitter almonds. It may be easily 
liquefied by a pressure of 4 atmospheres or a temperature of 
—25^ Its density is 1.8064 compared to air, or 2G compared 
to hydrogen. This is free cyanogen. 

It has separated from the mercury, which is condensed in 
little drops in the dome of the retort. The atom of mercury 
was combined with two groups (CN), which unite together 
when they separate from the mercury, and remain combined 
together in the gas which is disengaged. The latter contains 
CN combined with CN. Its formula is : 

NC-CN = (CN)2 = Cy^ 

2 volumes of this gas contain two atoms of carbon and two 
atoms of nitrogen. 

This composition may be demonstrated by cudiomctric analy- 
sis. 

2 volumes of cyanogen and 4 volumes of oxygen are intro- 
duced into a mercury eudiometer. On the passage of an electric 
spark there is a flash of blue light, and the volume of the gas 
is not changed. If a solution of potassium hydrate be now 
passed into the eudiometer, the six volumes of gas will be 
reduced to two. 

4 volumes of CO^ are formed ; 

2 volumes of N remain. 

2 volumes of cyanogen then contain the carbon contained in 200^, that 
\?, 02, and W. 

This is expressed by snying that the formula of cyanogen, C^N^ = Cy'^, 
corresponds to 2 volumes. 



HYDROCYANIC ACID. 431 

On contact with flame, cyanopjcn takes fire and burns in the 
air witli a purple flame, yieklinu' carbon dioxide and nitrogen. 

Water dissolves four and one-halt" times its volume of cyan- 
ogen. When this solution is left to itself it deposits brown 
flakes. It then contains in solution urea, ammonium carbonate, 
ammonium cyanide, and ammonium oxalate. 
C-'N'^ + 4ir-'0 = (NH^)'^C'^O^ 

Cyanogen. Ammonium oxalate. 

Cyanogen. Hydrocyanic acid. Cyanic acid. 

^2)N -h H'O = CO^ + Nff 

Cyanic acid. Ammonia. 

The ammonia formed by the latter reaction combines with 
the cyanic acid to form ammonium cyanate, which becomes 
converted into urea, as will be seen shortly. 

It is a curious fact that in the presence of a small quantity 
of aldehyde, the decomposition of an aqueous solution of 
cyanogen yields, almost entirely, but one product, — oxamide. 

C^N^ + 2H20 = C'^'<Nh' 

Oxamide. 

If a fragment of potassium be heated in cyanogen gas, a 
brilliant flash of light takes place ; in combining with cyanogen 
potassium becomes incandescent. Potassium cyanide is formed. 
(CN)^ -f K^ = 2KCN 

In this reaction, cyanogen combines directly with a metal. 
It acts as a simple element, such as chlorine. 

Paracyanogen, which has been mentioned before, is a poly- 
meride of cyanogen. When it is quickly heated to redness, it 
is entirely transformed into cyanogen gas. 

HYDROCYANIC ACID. 

(PRUSSIC ACID.) 
IICN = HCy 

Preparation. — Gray-Lussac prepared hydrocyanic acid by 
heating mercury cyanide with hydrochloric acid. 

An easier process consists in decomposing prussiate of potash 
(potassium ferrocyanide) with sulphuric acid. 8 parts of the 



432 ELEMENTS OF MODERN CHEMISTRY. 

sjilt in fine powder are heated in a retort with 9 parts of sul- 
phuric acid, previously diluted with 14 parts of water. 

The neck of the retort is inclined upwards, so that the aque- 
ous vapors are condensed and run back into the retort, while 
the vapor of prussic acid, which is very volatile, is dried by 
passage through a tube containing calcium chloride, and con- 
densed in a receiver placed in a freezing mixture of ice and 
salt. 

Properties. — This acid is a colorless, limpid, and very vol- 
atile li(|uid, having a penetrating odor resembling that of bitter 
almonds. Its density at 7° is 0.7058. It boils at 26.5°, and 
solidifies to a crystalline mass at — 15°. 

It scarcely reddens blue litmus-paper. On contact with an 
incandescent body, it takes fire and burns with a white flame 
lightly tinted with violet. 

It does not keep long in the pure state. It becomes brown, 
and is finally converted into a solid, brown mass. 

It dissolves in water in all proportions. A solution contain- 
ing 2 per cent, is used in medicine. 

When hydrocyanic acid is mixed with its own volume of 
concentrated hydrochloric acid, the mixture gets hot and soon 
deposits abundant crystals of ammonium chloride. The solu- 
tion contains formic acid. 

HCN + 2H^0 = CWO' + NH' 

Hydrocyanic acid. Formic acid. 

In reactions with the hydracids, hydrocyanic acid can function 
like a compound ammonia, N(CII)'" (formonitrile). It unites 
with elevation of temperature with hydrochloric, hydrobromic, 
and hydriodic acids to form compounds, such as N(CH)'". 
HCl and N(CH)'".HI, that may be compared to the ammo- 
nium salts. In these crystalline compounds, the anhydrous 
bases can displace the hydrocyanic acid, as they displace am- 
monia in the ammoniacal salts ; thus, 

N(CH)HC1 + NH^ = NH*C1 + HCN 

Cupric oxide displaces hydrocyanic acid in the same manner 
in the hydrobromide of formonitrile. 

The oxidized organic acids unite only with difficulty with 
hydrocyanic acid, and at an elevated temperature (Arm. 
Gautier). 

Hydrocyanic acid is one of the most rapid and most danger- 
ous of poisons. A single drop placed upon the eye of a rabbit 



METALLIC CYANIDES. 433 

is sufficient to kill the animal in a few instants, and after vio- 
lent convulsiions. 

Hydrocyanic acid may be detected by the follo\vin<2; tests : 

1. It gives a white precipitate of silver cyanide with silver 
nitrate, and this precipitate does not darken on exposure to 
light. When properly dried and heated, silver cyanide disen- 
gages cyanogen. 

2. If a drop of hydrocyanic acid be added to a mixed solu- 
tion of ferrous and ferric sulphates, and an excess of potassium 
hydrate be added, a thick, dark-colored precipitate is formed. 
If this be treated with an excess of hydrochloric acid, the fer- 
rous and ferric oxides precipitated will be dissolved, and Prus- 
sian blue will remain, strongly coloring the liquid. 

METALLIC CYANIDES. 

We will only consider the two more important metallic cya- 
nides, those of potassium and mercury. 

Potassium Cyanide, KCy = KCN. — This compound is 
prepared by heating well-dried potassium ferrocyanide to red- 
ness in stoneware retorts. After cooling, the black mass is 
exhausted with alcohol; this solvent leaves a black deposit, 
consisting of charcoal and iron, and the solution evaporated in 
vacuo deposits the potassium cyanide as a white, crystalline 
mass. 

This body crystallizes in cubes. It has a caustic taste and 
an after-taste of bitter almonds. It is very poisonous. It is 
quite soluble in water and alcohol. When its aqueous solution 
is boiled, it disengages ammonia, and is converted into potas- 
sium formate. This reaction takes place slowly in the cold, 
and is analogous to that which has before been described. 

When potassium cyanide is heated with sulphur, it is con- 
verted into potassium sulphocyanate. Iodine dissolves abun- 
dantly in a solution of potassium cyanide ; potassium iodide is 
formed, and cyanogen iodide is deposited in crystals. 

Solution of potassium cyanide dissolves the insoluble cya- 
nides of zinc, silver, etc., forming double cyanides. 

Mercury Cyanide, HgCy^ = Hg(CN)l — This compound 
is prepared by diwssolving finely-powdered mercuric oxide in an 
aqueous solution of hydrocyanic acid until the odor of the lat- 
ter has entirely disappeared, being careful to avoid an excess 
of the oxide. After concentration and cooling, colorless, anhy- 
T 37 



434 ELEMENTS OP MODERN CHEMISTRY. 

drous prisms are obtained, which are unaltered by air and light. 
This is mercury cyanide. It is very poisonous. 

It possesses a nauseous metallic taste, and dissolves in 8 
parts of cold water. 

It is decomposed by heat into mercury and cyanogen ; para- 
cyanogen is formed at the same time. The solution of mer- 
cury cyanide dissolves mercuric oxide, and forms with it a 
compound more soluble than the cyanide, crystallizing in color- 
less scales. 

If a solution of potassium iodide be added to a solution of 
mercuric cyanide, a compound of the two substances is imme- 
diately precipitated in beautiful pearly scales (Cailliot). 

FERKOCYANIDES. 

By this name are designated compounds containing cyanogen 
and iron intimately combined together and forming a complex 
radical capable of passing from one compound to another by 
double decomposition. This radical, which is called ferrocy- 
aiwgen, contains one atom of diatomic iron combined with six 
cyanogen groups, CN. As each of the latter represents one 
atomicity, it is evident that the group (Cy^-Fe)''', in which 
but two atomicities are saturated between the Fe and 2Cy, 
must be tetratomic. Hence ferrocyanogen can combine with 
four atoms of a inonatomic metal such as potassium. The im- 
portant compound known as potassium ferrocyanidc, or yellow 
prussiate of potash, has such a composition. 

Potassium Ferrocyanide, K^Cy^Fe -f 3H-0. — This salt is 
obtained by calcining animal matters, such as blood, horn, the 
debris of skin, leather, etc., in closed iron vessels with potassium 
carbonate. The calcined mass, which contains potassium cy- 
anide, is exhausted with boiling water, and ferrous sulphate is 
added to the solution, which is then evaporated to crystalliza- 
tion ; or the solution is boiled with metallic iron, which dissolves 
with evolution of hydrogen. The iron may also be added to 
the mixture of animal matter and potassium carbonate before 
calcination ; after cooling, the mass is pulverized and exhausted 
with ))oiling water. The solution contains ferrocyanide. 

When sufficiently concentrated, it deposits the salt in yellow 
crystals, which are derived from a s(juare octahedron. They 
are unaltered by the air, but lose 12.8 i)er cent, of water at 
100°. The anhydrous salt is white. 



POTASSIUM FERRICYANIDE. 435 

Potassium ferrocyanide dissolves in 2 parts of boiling, and 
in 4 parts of cold water. It is insoluble in alcohol. AVhen 
heated with bodies rich in oxyuen, such as nianuanesc dioxide, 
it is converted into potassium cyanate, the iron itself being 
oxidized to peroxide. It is not poisonous. 

When fused with sulphur, it is converted into potassium 
sulphocyanate. 

When heated with concentrated sulphuric acid, it yields pure 
carbon monoxide, and a residue consisting of sulphates of iron, 
potassium, and ammonium. 

Potassium ferrocyanide precipitates many metallic solutions. 
The following are some of these precipitates : 

Zinc ferrocyanide Zn2Cy6Fe, white. 

Copper ferrocyanide Cu-^Cy^Fe, mahogany color. 

Lead ferrocyanide Pb-Cy^Fe, white. 

Silver ferrocyanide Ag^Cy^Fe, white. 

Potassium ferrocyanide forms a bluish-white precipitate with 
ferrous salts. This precipitate contains : 

It is identical with the bluish-white deposit which is formed when 
potassium ferrocyanide is heated with dilute sulphuric acid. 

Prussian Blue, (re^j^Cy'Fe)^— This is the dark-blue pre- 
cipitate obtained when a solution of potassium ferrocyanide is 
poured into a ferric salt. 

2Fe2Cl« + 3KTy«Fe = 12KC1 -f re^Cy^Fey 

Ferric chloride. Potiissiiim lerrocjanide. Ferric ferrocyanide. 

(Prussian blue.) 

The Prussian blue of commerce ordinarily occurs in cubical 
fragments, having a fine blue color and a coppery reflection. 

When calcined in contact with the air, it leaves a residue 
of peroxide of iron. It is insoluble in water, alcohol, and in 
the weaker acids. Oxalic acid dissolves it, and the solution is 
employed as a blue ink. 

POTASSIUM FERRICYANIDE. 

(red prussiate of potash.) 

K6(Cy6Fe)2 

This beautiful salt, discovered by Leopold Gmelin, is formed 

when a current of chlorine is passed into a solution of potassium 

ferrocyanide. Potassium chloride and potassium ferricyanide 

are formed, and the latter gives to the liquid a deep green-brown 



436 ELEMENTS OF MODERN CHEMISTRY. 

color. On evaporation it deposits the new salt, which is puri- 
fied by a second crystallization. Potassium chloride remains 
in the mother-liquor. 

2K^(Cy«Fe) + CP = 2KC1 -f K''(Cy«Fe)2 

Potassium ferrocyanide. Potassium ferricyanide. 

Potassium ferricyanide forms magnificent clinorhombic prisms 
of a ruby-red color. These crystals are anhydrous. They con- 
tain K^Cy''^Fe^ It is considered that they contain a hexad 
radical, Cy^^Fc'^, formed by the union of two ferrocyanogen 
radicals '(FeCy^-Cy^Fe)^' =^ ferricyanogen. 

Potassium ferricyanide dissolves in 3.8 parts of cold water, 
and in a less quantity of boiling water. The solution has a 
dark yellow-brown color. It does not precipitate the ferric 
salts. In solutions of the ferrous salts it gives a blue precip- 
itate analogous to Prussian blue, and which is called TimihuU's 
blue. 
K\Cy'Fef + SFeSO* = SK'^SO* -f Fe='(C/Fe)2 

Potassium Ferrous sulphate. Potiissium Ferrous ferricyanide. 

.ferricyanide. sulphate. (TurnbuU's blue.) 

NITIiOFERROCYANIDES. 

These salts, which were discovered by Playfiir, are formed 
by the action of nitric acid upon certain alkaline ferrocyanides. 
The best known is sodium nifroferrocyanide^ or, as it is ordi- 
narily called, sodium nitroprusside. 

It is prepared by oxidizing potassium ferrocyanide with dilute 
nitric acid. After filtration and evaporation, crystals of potas- 
sium nitrate and a deposit of oxamide are obtained. The 
mother-li([uor is saturated with sodium carbonate, and on 
evaporation yields sodium nitroprusside, which may be purified 
by recrystallization. 

Sodium nitroferrocyanide crystallizes in large right rhombic 
prisms of a ruby-red color. Its composition is represented by 
the formula Na'Cy5(N0)Fe -f 2H'0. Its aqueous solution 
has a red-brown color, and gives a very intense but evanescent 
purple color with solutions of the alkaline sulphides. 

CHLORIDES OF CYANOGEN. 

There are two chlorides of cyanogen known, <a chloride, 
CyCl, which is liquid below 15.5°, and a solid chloride, Cy'^CP. 
These two chlorides present a curious instance of polymerism. 



CHLORIDES OF CYANOGEN. 43Y 

Liquid Cyanogen Chloride, CyCl ==: CNCl— Tliis coni- 
pound is prepared by passing chlorine gas over mercury cy- 
anide, or better, into an acpieous sohition of liydrocyanic acid, 
wliich is maintained at O'^. Hydrochloric acid and cyanogeu 
chloride are formed. 

HCN + CP = CNCl + HCl 

When the solution is saturated with chlorine, it is gently 
heated, and the cyanogen chloride which is disengaged is 
passed through a tube containing calcium chloride, and con- 
densed in a well-cooled receiver. 

When properly purified, cyanogen chloride is a colorless 
liquid, having a penetrating odor, which is very irritating to 
the eyes. It boils at 15.5° and solidifies at — 5 or — 6°. When 
pure, it can be preserved without alteration, but if it contain a 
trace of chlorine, it soon becomes converted into the solid 
chloride. 

SoUd Cyanogen Chloride, Cy'CP == O^N^CP.— This body 
results from the polymeric transformation which the liquid 
chloride undergoes spontaneously under certain circumstances. 
It can also be obtained by exposing hydrocyanic acid to the 
action of chlorine in direct sunlight. 

It crystallizes in brilliant, yellow needles or plates. It melts 
at 140° and boils at 190°. It has a peculiar, irritating odor. 
Boiling water immediately decomposes it into hydrochloric and 
cyanuric acids. 

C-'X^CP -[- SH^O = ^^^'JN^ + 3HC1 

Cyanogen chloride. Cyanuric acid. 

Cyanogen Bromide and Iodide. — The bromide and iodide 
of cyanogen correspond in constitution to the liquid chloride. 
They are obtained by the action of bromine or iodine upon 
mercury cyanide. These elements decompose mercury cyanide 
with formation of bromide or iodide of mercury, the excess 
of bromine or iodine combining with the cyanogen to form 
cyanogen bromide or iodide. 

Cyanogen hromide, CNBr, is solid and crystallizes in bril- 
liant cubes. It melts at 4° and vaporizes at 15°. 

Cyanogen iodide, CNI, sublimes spontaneously in beautiful 
colorless needles when a mixture of iodine and mercury cya- 

37* 



438 ELEMENTS OF MODERN CHEMISTRY. 

nido is placed in the bottom of a flask. Mercuric iodide is 
formed. Cyanogen iodide lias a penetrating odor ; it is very 
volatile and, like the chloride and bromide, is very poisonous. 

COMPOUNDS OF CARBON MONOXIDE. 

Carbon monoxide plays the part of a diatomic radical. It is 
capable of uniting with one atom of oxygen to form carbonic acid 
gas, or with two atoms of chlorine to form chlorocarbonic gas. 

It can also unite with two residues, NH'*, which are mon- 
atomic since they represent ammonia less one atom of hydro- 
gen ; lastly, it may unite with NH, which is diatomic since it 
represents ammonia minus two atoms of hydrogen. The com- 
pounds thus formed have the following constitutions : 
CO.O carbon dioxide. 

CI 
CO<^^j chlorocarbonic gas. 

CO(NH)" cyanic acid. 

The last two compounds can be considered as derived from 
the ammonia type. 

Cyanic acid is derived from one molecule of ammonia by 
the substitution of the diatomic radical CO, which is called 
carhonyl^ for two atoms of hydrogen. 

! f CO" 

H ^ i H cyanic acid. 

Urea is derived from two molecules of ammonia by the sub- 
stitution of the radical carbonyl for two atoms of hydrogen, 
r 112 ( CO" 

N2 ^ H2 N2 ^ H2 urea. 

( H2 ( H2 

Urea is then carhonic dlamide ; or more simply, carbamide. 

CYANIC ACID. 
CONH 

Liebig and Wohler obtained this acid by the dry distillation 
of cyanuric acid. One molecule of the latter, which is poly- 
meric with cyanic acid, then breaks up into three molecules of 
the latter body. 

C^O'N^H^ = 3C0NH 

Cyanuric acid. , Cyanic acid. 



CYANIC ACID. 439 

The latter acid condenses at a few degrees below 0° to a color- 
less liquid having a strong and irritating odor. It is very 
unstable. As soon as it is removed from the freezing mixture 
in which it is condensed, and its temperature rises to a few 
degrees above 0°, it produces a crackling noise and little ex- 
plosions, and is converted by a molecular transformation into 
an amorphous white mass called cyamelide. The latter body 
is also formed at the same time as cyanic acid by the dry distil- 
lation of cyanuric acid. 

Potassium Cyanate, KCON. — This salt is prepared by 
heating to dull redness in a flat sheet-iron dish an intimate 
mixture of '1 parts of potassium ferrocyanide and 1 part of 
manganese dioxide, both in fine powder and perfectly dry. 
The mixture must be continually stirred ; it blackens and 
enters into semi-fusion ; after cooling, it is reduced to powder 
and exhausted with hot alcohol of 80 per cent. On cooling, 
the filtered alcoholic solution deposits potassium cyanate in 
laminated, transparent crystals which are anhydrous. This salt 
is very soluble in water and but slightly soluble in cold concen- 
trated alcohol. If hydrochloric acid be added to an aqueous so- 
lution of potassium cyanate, carbonic acid gas is disengaged with 
brisk effervescence. The liquid contains ammonium chloride. 
CONH + H^O =^ CO' + Nff 

There is a compound isomeric with potassium cyanate ; it is 
formed by the action of cyanogen chloride upon potassium 
hydrate (Bannow). 

CN.Cl 4- 2K0H = KCl + H'O + KCNO 

Cyanogen chloride. Potassium cyanate. 

The hydrate corresponding to this potassium salt would be 
the true cyanic acid, of which the ethers were discovered by 
Cloez. The compound actually known by the name cyanic acid 
does not merit that name. It is not a compound of cyanogen, 
but a combination of oxide of carbon ; it is cai'hhnide. It should 
be called hocyam.c add. The following formulae will explain 
this curious isomerism: 

H-O-CIN H-N=C=0 

Cyanic acid. Isocyanic acid. 

K-O-C^N . K-N=C=0 

Potassium cyanate (Bannow). Potassium isocyanate (ordinary cyanate). 

en^-O-CEN C'H5-N=C=0 

Ethyl cyanate Ethyl isocyanate, 

(Cloez). (Cyanic ether of Wurtz.) 



440 ELEMENTS OF MODERN CHEMISTRY. 

Ammonium Cyanate. — This is formed when vapor of cyanic 
acid is passed into a flask containing ammonia gas. It is a solid, 
white mass, very soluble in water. When its aqueous solution 
is treated with hydrochloric acid, it disengages carbon dioxide 
like the solution of potassium cyanate. If its aqueous solution 
be boiled, or even left to itself for several days, ammonium 
cyanate becomes transformed into urea. 

(NHOCON = CO<^f' 

Ammonium cyanate. Urea. 

UREA. 

CH*N20 

This body, noticed by Rouelle in 1773, is the most abundant 
of the solid constituents of urine, from which it was extracted 
by Fourcroy and Vauquelin in 1799. Wohler was the first to 
obtain urea artificially by combining cyanic acid and ammonia. 

CONH + Nff = CH^N^O 

This discovery was the first instance of the synthesis of an 
organic body. 

Urea is also formed by the action of chlorocarbonic gas upon 
ammonia (Natanson). 

C0<^} + 2Nff = C0<^^', + 2HCi 

Also by the action of ammonia on ethyl carbonate. 

Ethyl carbonate. Urea. Alcohol. 

These reactions show clearly that urea is the amide corre- 
sponding to carbonic acid, that is, carbonic diamide. Indeed, 
it represents neutral ammonium carbonate, less two molecules 
of water. 

Preparation. — 1 . Urea may be obtained from urine by the 
following process. The urine is evaporated to a syrupy consist. 



UREA. 441 

enee on a water-bath. It is allowed to cool, and an excess of 
cold nitric acid is added ; a mass of crystals are formed, which 
ordinarily liave a brown color. They are drained, washed with 
a little ice-water, redissolved in hot water, and animal charcoal 
which has been washed with hydrochloric acid is added. The 
whole is heated on a water-bath for a few minutes and then 
filtered. Colorless crystals of urea nitrate are obtained on 
cooling. 

They are suspended in water, and a concentrated solution 
of potassium carbonate is added little by little, until all effer- 
vescence ceases. Carbon dioxide is disengaged, and potassium 
nitrate is formed, while the urea is set free. The liquor is 
evaporated to dryness on the water-bath, and the residue ex- 
hausted with absolute alcohol, which dissolves the urea, while 
the potassium nitrate remains. The alcoholic solution is con- 
centrated, and urea crystallizes out. 

2. Potassium cyanate is prepared by heating 28 parts of 
well-dried potassium ferrocyanide with 14 parts of manganese 
dioxide, as has been already indicated. The cooled mass is 
coarsely powdered, and exhausted with cold water, which dis- 
solves the potassium cyanate. 20 parts of ammonium sulphate 
are added to the filtered liquid, which is then evaporated to 
dryness on a water-bath. The residue is exhausted with boil- 
ing alcohol, which dissolves the urea and leaves potassium sul- 
phate. 

In this operation the potassium cyanate and ammonium sul- 
phate undergo double decomposition, with formation of potas- 
sium sulphate, and ammonium cyanate which is transformed 
into urea. 

Properties. — Urea separates from its aqueous solution in 
long, flattened, and striated prisms. It sometimes deposits 
from its alcoholic solution in square prisms. 

The crystals are colorless and possess a cooling taste. They 
dissolve in their own weight of water at 15°, and in 5 parts 
of cold alcohol of specific gravity 0.816. They are but slightly 
soluble in ether. 

If a solution of urea be added to a concentrated solution of 
chloride of lime, there is an abundant disengagement of gas, 
which is a mixture of nitrogen and carbon dioxide. The urea 
is entirely destroyed. 

CH^N^O -f H^O -f 3CP = CO^ + N^ -}- 6HC1 

IT»-3fr 



442 ELEMENTS OP MODERN CHEMISTRY. 

An aqueous solution of chlorine produces the same decom- 
position. 

Nitrous anhydride instantly destroys urea, with formation of 
water, carbon dioxide, and nitrogen. 

CH^N-'O ^- N^O^^ = CO^ + 2H^0 + 2N^ 

When an aqueous solution of urea is heated to 140° in a 
sealed tube, it absorbs the elements of water, and is converted 
into ammonia and carbon dioxide. 

CH*N^O + H^O = CO^ + 2NH3 

This conversion of urea into carbonate of ammonia takes 
place spontaneously in stale urine, under the influence of a 
peculiar ferment (Van Tieghem). 

Action of Heat on Urea. — Cyanuric Acid. — Urea fuses 
at 120°. When it is rapidly heated to a higher temperature, 
it disengages ammonia and leaves a white residue, which is 
ci/anuric acid. This body is tri-cyanic acid: 

(CO)=NH 

eO'N^H^ = (CO)=NH 

(CO)^NH 

It results from the combination of three molecules of cyanic 
acid, which are condensed into one, and held together by the 
nitrogen which each contains. This is indicated by the lines 
of union in the formula. Indeed, the three atoms of nitrogen 
are arranged in a sort of ring, so that each of them has an 
atomicity saturated by its neighbor. 

N 
/\ 

N— N 

Cyanuric acid is but slightly soluble in cold water. It sepa- 
rates from its boiling ac^ueous solution in small, colorless crys- 
tals, containing two molecules of water of crystallization. 

By dry distillation, it is converted into cyanic acid. 

Compounds of Urea with Acids. — If nitric acid be added 
to a concentrated solution of urea, the liquor assumes the form 
of a white, crystalline, laminated mass, composed of crystals 
of urea nitrate, CH^N^O.HNOl 



COMPOUND UREAS. 443 

These er3\stuls are soluble in water and alcohol. They 
stroniily redden litmus solution. They decompose at 140°, 
diseniiaiiini;- a large ([uantity of iras. 

Tiie hydrochloride of urea, ClPN-O.IICl, and the oxalate, 
(CH*N'^0)-C^ir-0*, are known. The latter salt precipitates in 
small, colorless, p-anular crystals when a concentrated solution 
of oxalic acid is added to a concentrated solution of urea. 

Compoimds of Urea with Oxides and with Salts. — There 
are several compounds of urea with mercuric oxide. They 
are formed either by the direct action of mercuric oxide upon 
urea, which dissolves that oxide, or by the reaction of mercuric 
chloride or nitrate upon urea, which is precipitated by both of 
these salts. A solution of urea converts recently-precipitated 
silver oxide into a gray powder, which is a compound of urea 
and oxide of silver. Among the compounds of urea with the 
various salts, that which it forms with sodium chloride is the 
most important. It crystallizes in colorless, oblique rhombic 
prisms, containing CH'N'-'O.NaCl -f H-Q. 

COMPOUND UREAS. 

The compounds which are derived from urea by the substi- 
tution of various alcoholic radicals for hydrogen are called 
compound ureas. They are obtained either by the action of 
cyanic acid upon the compound ammonias, or by treating the 
cyanic ethers with ammonia or with the compound ammonias 
(Ad. Wurtz). 



CONH + 




- C0<'^^^^'^'^ 


Cyanic acid. 


Ethylaniine. 


Ethylurea. 


C0N(C^H5) 


+ NH^ = 




Ethyl cyanate. 




Ethylurea. 


The following is the nomenclature and composition of some 



of the principal compound ureas : 



CH4N20 urea. 
CH3(CH'5)N20 methylurea. 
CH3(C2H5)js20 ethylurea. 
CH2(C2H5)2N20 diethylurea. 
CH(C2II5)3N20 triethvlurea. 
CH3(C5Hii)N20 amylurea. 
CH3(C6I15)N20 phenylurea. 
CH2(C6n5j22}20 diphenylurea. 



444 ELEMENTS OF MODERN CHEMISTRY. 

POTASSIUM SULPHOCYANATE. 

KCSN 

This salt, which is sometimes called potassium sulphocyanide, 
corresponds to the cyanate, in which the oxygen is replaced by 
sulphur. 

It is prepared by heating a mixture of two parts of potas- 
sium ferrocyanide and one part of sublimed sulphur to redness 
in a crucible or luted matrass. After cooling, the mass is 
dissolved in water, the solution filtered, and potassium carbon- 
ate added to the liquor as long as a precipitate of ferrous car- 
bonate is formed. The solution is again filtered, evaporated to 
dryness, the residue exhausted with alcohol, and the alcoholic 
solution allowed to evaporate spontaneously. 

Potassium sulphocyanate crystallizes in long striated prisms 
resembling potassium nitrate, or in needles terminated by four- 
faced points. It is deliquescent and very soluble in water and 
alcohol. 

Solution of potassium sulphocyanate produces an intense 
blood-red color with the ferric salts, due to the formation of 
ferric sulphocyanate. 

Ammonium Sulphocyanate, NH^CSN. — This body corre- 
sponds to ammonium cyanate. It occurs in the water from the 
purification of coal-gas. When heated to 170°, it is converted 

into sidplw-nrea^ CS<^tt2) fusible at 140° (Reynolds). 

The sulphocyanates present an isomerism exactly like that 
which has been mentioned for the cyanates. 



MONATOMIC ALCOHOLS AND THEIR 
DERIVATIVES. 

These compounds form part of the great class of alcohols. 
They are neutral hydrates, derived from hydrocarbons by the 
substitution of the radical hydroxyl OH for an atom of hydro- 
gen. Among these bodies, the more important are those which 
belong to the same series, as ordinary alcohol, or ethyl hydrate, 
which has been indicated on page 417. Wood-spirit, or methyl 
hydrate, is the simplest term of the series. While studying its 
combinations, in 1835, Dumas and Peligot were the first to call 
attention to the function " alcohol." 



METHANE. 445 



METHYL COMPOUNDS. 

In these compounds, we admit the existence of a radical, 
Ctr\ to which the name methyl is i;iven. Wood-spirit is its 
hydrate ; marsh gas, or methane, its hydride. To this hydride 
correspond a chloride, a bromide, and an iodide. Chloroform 
is dichloro-ni'jthylchloride, or trichloromothane. xVround methyl 
hydrate are grouped the salts of methyl or methylic ethers, re- 
sulting from the action of the acids upon that body, and which 
are to methyl hydrate as the potassium salts are to potassium hy- 
drate. They are the compound methyl ethers. The following 
formulne indicate the relations which exist between these bodies : 



CH 



Methane, or methyl hydride. Methyl hydrate. 

CH^ci ch'>^ 

Methyl chloride. Methyl oxide. 

CHCP ^ CIP^^ 

Chloroform. Methyl acetate. 

These compounds will be but briefly described. 

METHANE. 

(marsh gas.) 

The inflammable gas which is disengaged from the mud of 
marshes is impure methane. The same gas is frequently 
evolved in the galleries of coal mines, and constitutes the 
fire-damp of miners. It is produced artificially by the action 
of an excess of alkali upon acetic acid (Persoz, Dumas). 

Preparation. — Methane is most conveniently prepared in 
the pure state by strongly heating in a glass flask or retort a 
mixture of 1 part of sodium acetate, 1 part of potassium hy- 
drate, and li parts of lime ; the lime is added to prevent the 
action of the potassium hydrate upon the glass. The gas may 
be collected over water. 

NaC^H^O^ + NaOH = QW + Na^CO^ 

Sodium acetate. Methane. 

Properties. — Methane is a colorless, odorless gas. Its den- 

38 



446 ELEMENTS OF MODERN CHEMISTRY. 

sity is 0.559 ; it is but sliglitly soluble in water, somewliat more 
so in alcohol. It burns in the air with a yellow flame less lumi- 
nous than that of ethylene, or olefiant gas. A mixture of me- 
thane and oxygen explodes violently on the application of flame 
or the passage of an electric spark. 

If two volumes of methane and four volumes of oxygen be 
introduced into an eudiometer and the spark be piissed, a bright 
flash is visible. After the combustion, the mercury rises in the 
tube, and it is found that the volume of gas is reduced to one- 
third of the primitive volume (to 2 volumes) ; if a solution of 
potassium hydrate be introduced, the whole of the remaining 
gas will be absorbed. 2 volumes of methane produce in burning 
2 volumes of carbon dioxide, and require 4 volumes of oxygen. 
This experiment permits the determination of the composition 
of methane. 

2 volumes of carbon dioxide contain 2 volumes of oxygen 
combined with 1 volume (1 atom) of carbon; consequently two 
volumes of marsh gas contain one atom of carbon. 

The other two volumes of oxygen consumed have combined 
with four volumes of hydrogen, which are likewise contained in 
two volumes of methane. 

Consequently two volumes of methane contain 1 atom of 
carbon and 4 atoms of hydrogen. 

A mixture of chlorine and methane explodes when exposed to 
direct sunlight. In diffused daylight, the action is less violent, 
especially if an inert gas, such as carbon dioxide, be added. 
In this case, methyl chloride is formed, and in presence of an 
excess of chlorine, chloroform, and finally carbon tetrachloride. 

CH* + CP = HCl -f CH^Cl methyl chloride. 

CH* + 3CP = 3HC1 + CHCP chloroform. 

CH* + 4CP --= 4HC1 + CCP carbon tetrachloride. 

It is seen that in these reactions the chlorine is substituted 
for hydrogen, atom for atom. 

Inversely, when chloroform or carbon tetrachloride is sub- 
mitted to the action of nascent hydrogen, an inverse substitu- 
tion may be effected, and these chlorine compounds may be 
converted into methane. This may be accomplished by putting 
them in contact with sodium amalgam and water. The latter 
is decomposed by the sodium, and constitutes a source of hy- 
drogen (Melsens). 

CHCP H- 3H^ = 3HC1 + CH* 



METHYL HYDRATE — METHYL OXIDE. 447 



METHYL HYDKATE, OR METHYL ALCOHOL. 

(wood-spirit.) 
ClI^O = CIP-OH 

The products of tlie dry distillation of wood contain about 
one per cent, of a spirituous liquid, which was discovered in 
ISljJ by Taylor, and named wood-spirit. It is separated by 
several distillations and rectifications over lime ; for, being more 
volatile than the other products, it passes over first. 

When pure, it is a mobile, colorless liquid, having an alco- 
holic odor. It boils at 66.5°. Its density at 0° Is 0.8142 
(Dumas and Peligot). 

It is inflammable and burns with an almost colorless flame. 
It is miscible with water, alcohol, and ether in all proportions. 
It dissolves caustic baryta and forms with it a definite combi- 
nation. It forms a crystalline compound with calcium chloride 
containing CaCf' -f 4CH^0. 

Potassium and sodium react energetically upon methyl hy- 
drate ; the metal dissolves with disengagement of hydrogen and 
formation of potassium or sodium methylate. 

CH^-OH CH=^-OK 

Metliyl hydrate. Potassium methylate. 

If methyl alcohol be placed under a bell-jar containing also 
some watch-glasses filled with platinum black, so that the vapor 
of the wood-spirit mixed with air may come in contact with 
the finely-divided metal, it is found that the liquid soon becomes 
strongly acid. By the slow oxidation of the wood-spirit under 
these conditions, formic acid is produced (Dumas and Peligot). 

CH^-OH -f 0^ =. CHO-OH + H^O 

Methyl hydrate. Formic acid. 



METHYL OXIDE. 

(CH3)20 

When methyl alcohol is heated with twice its weight of 
concentrated sulphuric acid, a colorless gas is disengaged, which 
is methyl oxide. 

2CH10H = (Cff)^O -f- H^O 

Methyl hydrate. Methyl oxide. 



448 ELEMENTS OF MODERN CHEMISTRY. 

This gas is formed by the dehydration of methyl alcohol 
and the linking together of two methyl groups by an atom of 
oxygen. It is methylic ether. It holds the same relation to 
methyl hydrate that ordinary ether does to ethyl hydrate. 

It is colorless, very soluble in alcohol and ether, and quite 
soluble in water. It liquefies at a very low temperature 
(-30^). 

CHLORIDE, BROMIDE, AND IODIDE OF METHYL. 

These compounds may be regarded as marsh gas in which 
one atom of liydrogen is replaced by an atom of chlorine, bro- 
mine, or iodine. 

They are formed by the action of hydrochloric, hydrobromic, 
and hydriodic acids upon methyl alcohol. 

Cff.OH + HCl = CffCl + H'^O 

They may be considered as derived from the hydraclds by 
the substitution of the group methyl for the atom of hydrogen. 

HCl (CH^)Cl 

Hydrochloric acid. Methyl chloride. 

Methyl chloride is a colorless gas, having an agreeable odor. 
When exposed to intense cold, it condenses to a liquid which 
boils at — 22^. When heated for a considerable time with 
a concentrated solution of potassium hydrate, it is converted 
into methyl alcohol. 

Methyl bromide, CH^Br, is a colorless liquid, boiling at 
13°. 

Methyl iodide, CH^I, boils at 43° ; its density at 0° is 2.1992. 
It is made by gradually adding iodine to a mixture of methyl 
alcohol and amorphous phosphorus, and distilling. The dis- 
tilled liquid is mixed with water, which precipitates the iodide ; 
the dense liquid is separated, dried with calcium chloride, and 
distilled. 

CHLOROFORM. 
CHC13 

This important substance was discovered in 1831 by Soubei- 
ran and Liebig. It is made by distilling either alcohol or wood- 
spirit with a mixture of chloride of lime and calcium hydrate. 
The distilled liquid separates in two layers, of which the lower 



METHYL CYANIDE. 449 

is impure chloroform. It is separated, washed first with water 
and then with a sokition of potassium carbonate, and rectified 
over caUium chloride. 

Chloroform is a colorless, very mobile li((uid, havinpj an 
agreeable, ethereal odor. Its density is 1.48, and it boils at 
60.8°. It does not take fire on contact with flame. 

It is but sliglitly soluble in water, but dissolves readily in 
alcohol and ether. It dissolves sulphur, phosphorus, fats, 
resins, a great number of the alkaloids, and in general, organic 
matters rich in carbon. 

By the prolonged action of chlorine, it is converted into 
carbon tefrdcJiIoride, CCP, a colorless liquid boiling at 77°. 

A boiling alcoholic solution of potassium hydrate converts it 
into formate and chloride. 

CHCP + 4K0H = 2W0 -]- 3KC1 + KCHO^ 

Chloroform. Potiissiuni formate. 

When chloroform is boiled with an alcoholic solution of 
ethylate of sodium, sodium chloride is formed, together with 
an ethereal compound, CH(OC'^H^)-\ in which 3 oxethyl groups, 
OC"^!!^, replace the 3 chlorine atoms of chloroform (Kay). 

CHCP -f- 3XaO.C'H^ = 3NaCl -f CH(0C2H^/ 

Chloroform. Sodium ethylate. Kay's etlier. 

Chloroform, heated to 180° with aqueous or alcoholic ammo- 
nia, yields ammonium cyanide and sal-ammoniac. This re- 
action takes place at 100°, in presence of potassium hydrate. 
CHCP -f 5NH^ = NH^CN + 3NH*C1 

Chloroform acts in a remarkable manner upon the phenols 
in presence of an alkali such as soda or potassa, forming aro- 
matic aldehydes. This reaction, discovered by Reimer, will be 
described farther on (see Phenol). 

Chloroform is much employed in surgery as an anaesthetic. 
The inhalation of its vapor produces insensibility and loss of 
muscular action. 

METHYL CYANIDE. 

C2H3N =CH3Cy 

This body may be obtained by distilling a mixture of potas- 
sium methylsulphate and potassium cyanide, or by distilling 
acetamide with phosphoric anhydride, which removes one mol- 
ecule of water from the former body. 

38'^ 



450 ELEMENTS OF MODERN CHEMISTRY. 

CTr^o.Nir^ — H'o = en^N 

Acetauiide. Methyl cyKiiide, or 

iicetoiiitrile. 

The product obtained in the latter operation is called ace- 
tonitrile. 

diethyl cyanide is a colorless liquid, having a disagreeable 
odor ; it boils at 77°. A boiling solution of potassium hydrate 
decomposes it into ammonia and potassium acetate. 

CIP-CN + 2IP0 = CH^-CO.OH + NH^ 

Methyl cyanide. Acetic acid. 

Grautier has discovered an isomeride of methyl cyanide, 
methyl carhylainuie. This body is formed, together with 
methyl cyanide, when a mixture of potassium meth3lsulphate 
and potassium cyanide is distilled. Under the influence of alka- 
lies, it decomposes into formic acid and methylamine. 

^, j N + KOH + H^O = KCHO + ^^, \ N 

Methyl caibylamine. Potassium lomiate, Methylaiuiiie, 

METHYL NITRATE. 

CH3.N03 

This substance, which represents nitric acid in which the 
basic hydrogen is replaced by methyl, is an example of a com- 
pound methyl ether. 

It is prepared by introducing into a retort 50 grammes of 
powdered potassium nitrate, and adding a mixture of 100 
grammes of sulphuric acid and 50 grammes of wood-spirit. 
The reaction begins in the cold, but must be fiiushed by dis- 
tilling on a water-bath. The liquid condensed in the receiver 
is washed with water, and rectified several times over a mix- 
ture of massicot and calcium chloride. 

It is a colorless, neutral liquid ; density, 1.182 ; boiling-point, 
G6°. Its vapor explodes violentl}^ when heated above 150°. 

Methyl nitrate dissolves in ammonia, producing ammonium 
nitrate and methylamine. 

CHINO^^ + 2NH3 = NH\NO^ + CH^^CNH^ 

METHYL NITRITE AND NITROMETHANE. 

These two compounds present a remarkable instance of 
isomerism in very simple combinations. 

The first, CH''O.NO, which represents nitrous acid, HNO^ 



METHYL NITRITE AND NITROM ETHANE. -151 

in which the hyJn)i>eii is rephieed by methyl, is obtained when 
methyl alcohol is heated with nitric acid in presence of copper. 
It is a lit[uid boiling- at about — 12°. 

The second, called also nitrocarbol^ represents methane, in 
which an atom of hydrogen is replaced by the group (NO'")'. 
CH* CrF(NO0 

Methane. Nitroinotliane. 

It is obtained by the action of potassium nitrite upon potas- 
sium monochloracetate (Kolbe). 

CIl^CI.CO'^K + KN02 + H^O = KCl + CHi(NO'^) + KIICO^ 
Potassiuin mono- Potassium Nitromethaiie. 

chloiacetate. nitrite. 

It is also produced by the action of silver nitrite on methyl 
iodide (Y. Meyer). 

Nitromethane is a liquid boiling between 101 and 102°. It 
has an acid character, and one of its hydrogen atoms may be 
replaced by sodium. 

Nitromethane is clearly distinguished from methyl nitrite by 
the following property : nascent hydrogen transforms nitrome- 
thane into methylamine, a reaction which does not take place 
with its isomeride. 

CHXNOO + 3H^ = CHlNff -f 2ffO 

Nitromethaae. Methylamine. 

METHYLNITROLIC ACID. 

This remarkable combination has been obtained by Y. Meyer 
by the action of nitrous acid upon nitromethane. 

Cff(NO^^ + NO.OH = CH<x^^Qjj + H^O 

It is seen that in this compound two atoms of hydrogen of 
the methyl group CH^, are removed by an atom of oxygen of 
the nitrous acid, and replaced by the residue (N.OH). 

Methylnitrolic acid is prepared by dissolving 5 grammes of 
nitromethane in water, and adding first a dilute solution of 
potassium nitrite cooled to 0°, then dilute sulphuric acid also 
cooled to 0°, and finally dilute solution of potassium hydrate 
as long as the red color persists. At this moment, sulphuric 
acid is again added until the liquid is decolorized ; the solution 
is then saturated with calcium carbonate, and agitated with 
ether, which dissolves the methylnitrolic acid. 



452 ELEMENTS OF MODERN CHEMISTRY. 

After the evaporation of the ether, the acid remains as large, 
transparent, colorless prisms, fusible at 54°, but decomposing 
at the same time into formic acid and nitrogen. Dilute sul- 
phuric acid decomposes methylnitrolic acid into formic acid and 
nitroi'en monoxide. 

o 

CH^N^O^ = CH-'O^ -f N^O 

Formic acid. Nitrogen monoxide. 

The crystals decompose spontaneously in a few days. 



FULMINATES OF MERCURY AND SILVER. 

Among the important compounds related to the more simple 
organic combinations are those explosive salts known as fulmi- 
nates of mercury and silver. 

They are obtained by dissolving mercury or silver in nitric 
acid and adding alcohol to the still hot solution. In a few 
minutes a brisk effervescence takes place, and fulminate of 
mercury or of silver is deposited as a white, crystalline precip- 
itate. When dry, these bodies explode violently by either heat 
or percussion. Fulminate of mercury is the basis of percus- 
sion-caps. 

The composition of these salts is interesting; fulminate of 
mercury contains a monatomic group, (NO'^), a cyanogen group, 
(CN), and an atom of mercury, all three being united to an 
atom of carbon, of which the four atomicities are thus perfectly 
satisfied. 

Fulminate of silver has an analogous composition, but con- 
tains two atoms of silver. 

The fulminates may thus be grouped with organic compounds 
containing one atom of carbon, especially with the cyanide of 
methyl (Kekule). The following are some of these com- 
pounds : 



C H H 


H 


H 


methane. 


C H H 


H 


Cy 


methyl cyanide. 


C(N02) H 


H 


H 


nitroinethane. 


C(N02) H 


H 


Na 


sodium -nitromethane. 


C(N02) H 


H 


CI 


chloro-nitromethane. 


C(N02)C1 


CI 


CI 


trichloro-nitromethane (chloropicrin), 



C(N02)(N02)(N02)H nitroform. 
C(N02)* tetranitromethane. 

C(N02) Ag Ag Cy fulminate of silver. 
C(N02) Hg" Cy fulminate of mercury. 



CACODYL. 453 



CACODYL, OR DIMETHYLARSINE. 

As2(CH3)* 

This interesting compound has long been known in an im- 
pure state. In 1760, Cadet, demonstrator of chemistry at the 
Jardin-du-Roi, distilled a mixture of potassium acetate and 
white arsenic (arsenious oxide). He collected in the receiver 
an oily liquid, having an extremely offensive odor, and pro- 
ducing dense white fumes in the air. Hence the n^moi fuming 
liquor of Cadet. 

Bunsen's investigation into the chemistry of this body and 
its combinations has become classic. According to his re- 
searches, the fuming liquor of Cadet is a mixture of two bodies, 
one of which, containing only carbon, hydrogen, and arsenic, 
plays the part of a radical : it is cacodyl ; the other body is the 
oxide of this radical. 

To obtain cacodyl in the pure state, the crude product is 
treated with hydrochloric acid, which converts the oxide of 
cacodyl into chloride. 

As2(CH3)*0 -f 2HC1 = 2As(CH3)2Cl + H'^0 

Dimethylarsine oxide. Dimetliylarsine chloride. 

This chloride, separated by distillation, and treated with zinc 
at 100° in sealed tubes, furnishes free cacodyl. 

The latter is a dense liquid boiling at 170°, and having a 
penetrating arsenical odor. It is very poisonous. It produces 
dense white fumes in the air, even taking fire spontaneously. 
Its vapor density is 7.101. 

According to this vapor density, free cacodyl should be rep- 
resented by the formula As^CH^)* = (CH=^/As-As(CH^)l 

Arsenic being either triatomic or pentatomic it is seen that 
cacodyl is not saturated ; hence it can directly fix chlorine, 
oxygen, etc., yielding two series of compounds. Thus, one 
molecule of cacodyl, As^Me*, can fix 1 or 3 molecules of chlo- 
rine, forming the two chlorides : 

As2Me4 + CP = 2AsMe2Cl 
As2Me* + 3C12 = 2AsMe2Cl3 

To the two chlorides correspond the bromides, iodides, oxides, 
sulphates, etc. The oxides are 

Cacodvl oxide [As(CH3,2]20 
Cacodjlic acid As(CH3)20.0H 



454 ELEMENTS OF MODERN CHEMISTRY. 

Independently of the cacodyl compounds, other combinations 
of arsenic and methyl are known, — the methylarsines and the 
compounds of methylarsonium. 

These bodies form two series, which were discovered and 
studied by Baeyer, and which belong to the type AsX^ and 
xVsX^. The compounds of the first kind are not saturated, and 
can combine with Cl'^, or the equivalent of CP, passing into the 
state of the saturated compounds of the series AsX*. 

Series AsX^ Series AsX^ 

As(CH3y^ As(CH3)4CI 

Trimctliylarsiiie. Tetrametliylarsouium chloride, 

As(CH3)2Cl As(CH3)3C12 

Dimetliylursine nionochloride. Trimcthylarsiiie dichloride. 

As(CH3)Cr^ As(CH3)2C13 

Monompthylarsine dichloride. Diiiiethylarsine trichloride. 

AsCl^ As(CH3)CH 

Arsenic trichloride. Monomethylarsine tetrachloride. 

[AsCI^J 

It is worthy of remark that the trichloride of arsenic is 
incapable of fixing CP, and passing into the state of penta- 
chloride. 

These compounds need not be described. It may only be 
mentioned that trimethylarsine, As(CH'* )'^, is formed, together 
with cacodyl, by the action of methyl iodide on sodium arsenide. 
It is a liquid boiling below 100"^. 



ETHYL COMBINATIONS. 

The monatomic residue (C^H^)' = C'lP — H, which is the 
radical of ordinary alcohol, is called ethyl. Numerous com- 
pounds are known into which the radical enters. 

AVhen combined with hydrogen, it forms a gas, C^H*, which 
is ethyl hydride or ethane. The chloride, bromide, iodide, and 
cyanide of ethyl were formerly designated as simple ethers. 

Q,nV>C\ ethyl chloride. 

CnPBr ethyl bromide. 

CnV^l ethyl iodide. 

C^H^.CN ethyl cyanide. 

Ordinary alcohol is the hydrate, ether is the oxide of ethyl. 

C2n5-OH ethyl hydrate (alcohol). 

C2I15-0-C2I15 =^ (C21I5)20 ethyl o.xide (ether). 



ETHYL HYDRATE. 455 

The neutral compound ethers are derived from the corre- 
spondinii' acids by the substitution of the radical C'"H^ for their 
basic hydrogen. 

c^u'^o-OH cnpo-ocni^ 

Acetic acid. Ethyl aci'tuto. 

c^o^jOJJ c.o.jO:gll? 

Oxalic acid. Ethyl oxalate. 

( OH r o.cnp 

po i oh po \ o.c2h5 

(oh (o.cmp 

Phosphoric acid. rhosphoric ether (tiiethyl phosphate). 

Ethyl exists in the most diverse combinations. It can re- 
phice the hydrogen of ammonia, forming ethylated bases. It 
can unite with the metalloids and metals. 

Free Ethyl, or Butane, C*H'". — When it is sought to obtain 
free ethyl by heating ethyl iodide to 150° with zinc in sealed 
tubes, the radical combines with itself, its molecule being doubled 
(Frankland). 

2C'H^I + Zn = ZnF + (C'll'f 

A gas is thus formed which liquefies at -}-l°. It was 
formerly named free ethyl, but is the hydride of butyl, or 
butane. Indeed, it is incapable of regenerating ethyl compounds 
containing the simple radical (C'H^). When treated with bro- 
mine, it yields hydrobromic acid and a bromide C^H^Br^, which, 
according; to Carius, is identical with butylene bromide. 

Ethyl Hydride, or Ethane, C^H« =^ CH^-CHl— Frank- 
land obtained this gas by treating zinc-ethyl with water. 

Zn(C^Hs/ + 2H^0 = 2Cm' + Zn(OH)^ 

Zinc ethyl. Ethane. Zinc hydrate. 

It is a colorless gas, burning with a slightly blue, luminous 
flame. When treated with chlorine, it yields ethyl chloride 
and hydrochloric acid. 

ETHYL HYDRATE, OR ALCOHOL. 

Cm^O = CH3-CH2.0H 

Alcohol is the product of the fermentation of solutions which 
contain glucose, or a substance capable of transformation into 
glucose. 

It may be formed synthetically in various manners: 

1. By passing ethylene gas into sulphuric acid (Hennel and 



IPO = C'H^.OH -I- H^SO* 



456 ELEMENTS OP MODERN CHEMISTRY. 

Faraday) and boiling the ethylsulphuric acid so formed (Ber 
thelot). 

Ethylene. Ethylsulphuric acid. 

Ethylsulpliuric acid. Alcohol. 

2. By heating ethylene gas with hydriodic acid and decom- 
posing the ethyl iodide so formed with potassium hydrate (Ber- 
thelot). 

C'H* -I- HI =: C^IPI 

C^H^I + KOH = C'H^OH + KI 

3. By bringing aldehyde in contact with sodium amalgam in 
presence of water. The nascent hydrogen formed in this case 
fixes upon the aldehyde, converting it into alcohol (A. Wurtz). 

c^H^o + H^ ---= cni^o 

Aldehyde. Alcohol. 

Preparation and Purification of Alcohol. — Alcohol is 
manufactured by distilling fermented liquors, such as wine, 
fermented juice of beet-roots, and the product obtained from 
the fermentation of malt, which is saccharified barley, corn, or 
other grain. The apparatus now used for this operation has 
reached such a degree of perfection that alcohol of 95 per cent, 
may be obtained immediately by one distillation. 

Absolutely pure alcohol is obtained by rectifying the alcohol 
of commerce over substances avid of water, such as anhydrous 
potassium carbonate, quick-lime, or caustic baryta. The last 
portions of water are removed, and absolute alcohol obtained 
by redistilling the rectified alcohol with caustic baryta. Or 
some sodium may be dissolved in the alcohol, which may then 
be rectified on a water-bath. 

Properties. — Alcohol is a colorless, mobile liquid, having an 
agreeable, spirituous odor. Density at 0°, 0.8U95. Boiling- 
point, 78.4° at the normal pressure. 

Alcohol mixes with water and ether in all proportions. Its 
mixture with water takes place with elevation of temperature 
and contraction of volume. The maximum contraction takes 
place when the two bodies are mixed in the proportion of one 
molecule of alcohol (53,94 parts) to three molecules of water 
(49.84 parts). 



ETHYL HYDRATE. 457 

Alcohol absorbs moisture when exposed to the air. It dis- 
solves many nasos, litjuids, and solids. Tinctures arc solutions 
of various medicinal substances in alcohol. 

Among the simple bodies which are soluble in alcohol may 
be mentioned iodine. Potassium and sodium h^nlrates dissolve 
in it readily, and it is the same with most of the mineral acids. 
Many of the chlorides are soluble in alcohol ; such are those of 
calcium, strontium, zinc, and cadmium, ferric, cupric, mercuric, 
and auric chlorides. 

Alcohol dissolves the natural alkaloids, the essential oils, 
resins, and fatty bodies, the latter, however, less readily than 
ether. 

Decompositions. — When vapor of alcohol is passed through 
a red-hot porcelain tube, it is decomposed into water, carbon 
monoxide, hydrogen, methane, and ethylene. Besides this, 
carbon is deposited in the porcelain tube, and a small quantity 
of naphthaline is produced (Th. de Saussure), as well as 
benzol and phenol (Berthelot). The principal products of 
the decomposition of alcohol at a dull-red heat are methane, 
hydrogen, and carbon monoxide. 

C^H^'O := CO + CH* + H^ 

On the application of a burning body, alcohol takes fire 
and burns with a slightly luminous, bluish flame. On contact 
with platinum black, alcohol vapor mixed with air undergoes a 
slow combustion, which produces successively aldehyde and 
acetic acid. 

en^o + == C^H*0 + H^O 

Alcohol. Aldeliyde. 

C'H^O + = C^H^O^ 

Aldehyde. Acetic Acid. 

Acetic ether and a small quantity of a volatile, neutral body, 
called acetal, are at the same time formed as accessory products 
(Stas). 

The lamp without flame of Dbbereiner depends upon the 
slow combustion of alcohol. The wick of an ordinary spirit- 
lamp is surmounted by a spiral of platinum wire, so that when 
the lamp is lighted the spiral is heated to incandescence. If 
then the flame be extinguished, by covering it for an instant 
with a test-tube, the alcohol vapor continues to rise with the 
air around the still hot spiral, and undergoes a slow combustion. 
But the latter develops heat, and the spiral rapidly becomes 
u 39 



458 ELEMENTS OF MODERN CHEMISTRY. 

heated to incandescence, and if the current of air be regulated 
by a small glass chimney, the experiment may continue as long 
as the wick emits vapor of alcohol in sufficient (juantity. 

Bodies rich in oxygen oxidize alcohol at ordinary tempera- 
tures ; such are chloric and chromic acids. If a little alcohol 
be poured upon some chromic acid placed upon a brick, the 
liquid is immediately inflamed and the chromic acid reduced 
to chromium oxide. 

Chlorine attacks alcohol with great energy, the final product 
of the reaction being a body which has received the name 
chloral (Liebig, Dumas). 

If a small piece of potassium or sodium be thrown into pure 
alcohol, the metal soon melts, and then dissolves with disen- 
gagement of hydrogen. The product of the reaction is a crys- 
talline, solid matter which is ethylate of potassium or sodium, 
that is, a body derived from alcohol by the substitution of an 
atom of an alkaline metal for an atom of hydrogen. 

C-'H>0 C^IP>0 C=»:>0 

Alcohol. Potassium ethylate. Sodium ethylate. 

TJses of Alcohol. — Alcohol is used as a combustible in spirit- 
lamps. In the arts, it is employed in the manufacture of ether, 
chloroform, eau de cologne, and many other products. It is 
largely used in the laboratory, and in pharmacy, as a solvent ; 
it serves for the preservation of anatomical specimens. In 
France and England, alcohol employed for certain industrial 
uses is exempted from part of the tax, when it has previously 
been mixed with about one-tenth of wood-spirit and a few 
per cent, of mineral oils and resin. Such a mixture is unfit 
for the manuficture of brandy and liquors, but its usefulness 
as a solvent is in many cases unimpaired. 

Alcohol exists in fermented liquors, such as wine, cider, and 
beer. It is contained in much larger quantities in brandies, 
whiskeys, and spirits. These are products of the distillation of 
various alcoholic liquids. They are more or less rich in alco- 
hol. Brandy is prepared by the distillation of wine, cider, or 
the products of fermentation of cherry -juice (cherry-brandy), 
sugar-cane (rum), beet-root molasses (beet-brandy). Whiskey 
is distilled from fermented starchy materials, such as corn, rye, 
])()tat<)es, etc., the starch being first saccharified. The richness 
of these materials in alcohol is indicated by the degrees of an 



ETHYL OXIDE. 459 

alcoholometer. The following table gives the strength of some 
of these liquors. 

Percf.ntare of 
Cartier's Areometer. Alcohol. 

by volume. 

Weak brandy 16° 37.9 

Proof spirits 19° 60.1 

Strong brandy 22° 69.2 

Ordinary alcohol 33° 85.1 

Rectified alcohol (strongest commercial) 40° 96, 

Absolute alcohol 41.2° 100. 

ETHYL OXIDE, OR ETHER. 
(C2H5)20 = CH3-CH2-0-CH2-CH3 

If ethyl iodide be added to an alcoholic solution of ethylate 
of sodium and a gentle heat be applied, a deposit of sodium 
iodide is formed and vapors are disengaged which may be con- 
densed in a cooled receiver into an ethereal liquid. It is 
oxide of ethyl. 

mm + c^H^>o = Nai + gH;>o 

Etliyl iodide. Sodium ethylate. Ethyl oxide. 

If, in the preceding experiment, the ethyl iodide be replaced 
by methyl iodide, an extremely volatile liquid will be formed, 
which is the double oxide of methyl and ethyl. 

CH3I + C^^>0 = Nal + CW^o 
Methyl iodide. Oxide of methyl and ethyl. 

These classic experiments, due to Williamson, show that 
the oxide of ethyl contains two ethyl groups. It may be 
regarded as alcohol in which the hydrogen atom of the group 
hydroxyl is replaced by ethyl. 

H-O-H C^H^-O-H C^H^-0-C^H^ 

Water. Alcohol. Ethyl oxide. 

Preparation. — Ether is prepared in the arts by the action 
of sulphuric acid on alcohol. A mixture of 9 parts of con- 
centrated sulphuric acid and 5 parts of alcohol of 90 per cent, 
is heated in a flask, A (Eig. 122), and a small, continuous 
stream of alcohol is allowed to flow into this mixture through 
the funnel-tube a. The temperature of the liquid, indicated by 
the thermometer t, should not exceed 140 or 145°. The vapor 
disengaged is condensed in a Liebig's condenser, B, through 
which a stream of cold water flows continually. Under these 



460 



ELEMENTS OF MODERN CHEMISTRY. 



conditions, a mixture of ether and water collects in the re- 
ceiver D, together with a little alcohol, and towards the close 
of the operation, a small quantity of sulphurous acid gas is 
disengaged. The product is purified by washing with milk of 
lime, and then with pure water, after which it is rectified over 
calcium chloride on a water-bath. Fig. 122 represents the 
apparatus used for public demonstration ; in the arts, the opera- 
tion is conducted on a large scale in apparatus of an analogous 
construction. 




Fig. 122. 

Theory of Etherification. —The transformation of alcohol 
into ether is a true dehydration, brought about by the sul- 
phuric acid. 

2(C^H^0H) = (C'H^yO + H^O 

Williamson clearly proved that it is effected in two distinct 
phases ; in the first, ethylsulphuric acid and water are formed. 



Alcohol. 



J{>SO* = ^'^{j'>SO* + H20 
Sulphuric acid. Ethylsulphuric acid. 



ETHYL OXIDE. 401 

111 the second, another molecule of alcohol reacts with the 
ethylsulphuric acid ; ether is formed and sulphuric acid is 
regenerated. 



"O^ 



Ethylsulphuric acid. Alcohol. Ether, Sulphuric acid. 

Hence the ether and water collected in the receiver are pro- 
ducts of two distinct phases of the reaction. Ethylsulphuric 
acid is continually formed and as continually decomposed, 
regenerating sulphuric acid ready to act upon new por- 
tions of alcohol. However, although the operation is con- 
tinuous, it cannot go on indefinitely, for the mixture blackens 
after a time and becomes unfit to etherify new quantities of 
alcohol. 

Properties of Ether. — Ether is a colorless, very mobile 
liquid ; its taste is at first burning, then cooling ; its odor is suave 
and agreeable, and is called ethereal. Density at 0°, 0.73G6. 
Boiling-point under the normal pressure, 34.5°. * 

It is but slightly miscible with water, on the surflice of which 
it forms a separate layer. 9 parts of water dissolve 1 part of 
ether ; 36 parts of ether dissolve 1 part of water. Ether dis- 
solves in all proportions in alcohol and in methyl alcohol. 

It slightly dissolves sulphur and phosphorus, and notable 
quantities of bromine, iodine, ferric, mercuric, and auric chlo- 
rides, and many organic bodies, such as the oils, fats, resins, 
alkaloids, etc. 

It is very inflammable and burns with a quite luminous 
flame. Its vapor explodes violently when mixed with air or 
oxygen and ignited. 

If a heated spiral of platinum wire be suspended in a glass 
jar containing a little ether, in such a manner that the lower 
extremity of the wire is but a little distance from the surface 
of the liquid, the wire will soon become brightly incandescent 
and will ignite the ether. 

This effect is due to the ether vapor, which, coming in con- 
tact with the platinum, and being mixed with air, undergoes a 
slow combustion. Heat is thus developed, and the wire be- 
comes incandescent. 

Chlorine acts on ether with extreme energy. If the action 
be moderated, various products of substitution are obtained, 
among which the following have been well studied : 

39* 



462 ELEMENTS OF MODERN CHEMISTRY. 

Monochloretbcr ^ c^h^-^*^ liquid boiling at 98-99°. 

Dichlorether ^^^^2H5>^ liquid boiling at 140-147°. 

Tetrachlorether C2H'*C1''^^*^ liquid, density 1.5. 

Perchlorether C"2CI5^^ colorless crystals, fusible at 69°. 

The last is a solid body, crystallizing; in octahedra. By the 
action of heat it is decomposed into carbon sesquichloride and 
perchloraldehyde (Malaguti) . 

Perchlorether, Carbon sesquichloride. Perchloraldehyde. 

When two parts of bromine are added to one part of ether, 
and the mixture is cooled, a garnet-colored liquid separates 
and soon crystallizes. It is a compound of bromine and ether, 
(C'^H^)20.Br^, which crystallizes in thin, red plates, fusible at 
22° ; it is easily decomposed (Schiitzenberger). 



SULPHYDRATE AND SULPHIDE OF ETHYL. 

Two bodies are known which are intimately related, as re- 
gaTds their constitutions, with alcohol and ether. They are 
the sulphydrate and the suljiliide of ethyl. The first, formerly 
known as mercaptan, represents alcohol containing an atom of 
sulphur instead of an atom of oxygen ; the second represents 
ether in which the oxygen atom is replaced by sulphur. 

c^H^OH (cm^yo 

Ethyl hydrate. Ethyl oxide. 

c^H^SH (cmys 

Ethyl sulphydrate. Ethyl sulphide. 

Ffhi/l sulpliydrate is obtained by distilling a concentrated 
aqueous solution of potassium sulphydrate with a solution of 
potassium ethylsulphate. 

It may also be prepared by passing vapor of ethyl chloride 
into an alcoholic solution of potassium sulphydrate. The liquid 
is distilled as soon as it is saturated with ethyl chloride, and 
water is added to the distillate. Ethyl sulphydrate separates. 

KSH -\- en^ci = KCi + eH\sH 

Potassium sulphydrate. Ethyl chloride. Ethyl sulphydrate. 



ETHYL CHLORIDE. 463 

Ethyl sulpliydrate is a transparent, colorless liquid, very mo- 
bile, and having a fetid odor. Density at 21°, 0.835. Boil- 
ing-point, 30.2° (Liebig). 

It reacts energetically with mercuric oxide, forming water 
and a white, crystalline body which represents ethyl sulpliy- 
drate in which the hydrogen is replaced by mercury. Hence 
the name mercaptiui (mercurium captans), given to the sulphy- 
drate of ethyl by Zeise. This mercuric compound is insoluble 
in water; it contains (C-H'S)-Hg". 

Ethyl sulphide is obtained, like the sulpliydrate, by double 
decomposition. Vapor of ethyl chloride is passed into an alco- 
holic solution of potassium monosulphide. 

K^S -f 2C'^ffCl = 2KC1 -f {Q'Wf^ 

Potassium sulphide. Ethyl chloride. Ethyl sulphide. 

Ethyl sulphide is a colorless liquid, having a garlicky odor. 
It boils at 75°. It is insoluble in water. 



ETHYL CHLORIDE. 
C2H5C1 

This body is prepared by saturating alcohol with hydrochloric 
acid gas and distilling on a water-bath. Ethyl chloride is dis- 
engaged, and should be passed first through a wash-bottle and 
then through a tube containing calcium chloride, after which it 
may be condensed in a receiver placed in a freezing mixture. 

Below 11° ethyl chloride is a mobile, colorless liquid, having 
a penetrating and agreeable odor. It boils at 11° ; it is inflam- 
mable, and burns with a flame tinged with green. 

If some solution of silver nitrate be agitated in a jar con- 
taining vapor of ethyl chloride, no precipitate will be formed; 
but if the agitation be continued after the vapor has been 
ignited, an abundant precipitate of silver chloride will be 
formed, owing to decomposition of the silver nitrate by the hy- 
drochloric acid produced by combustion of the ethyl chloride. 

Ethyl chloride produces a precipitate of silver chloride when 
passed into an alcoholic solution of silver nitrate. 

Chlorinated Derivatives of Ethyl Chloride. — When ethyl 
chloride is submitted to the action of chlorine, various com- 
pounds are successively formed by the substitution of chlorine 
for hydrogen, atom for atom. The following is the nomencla- 



464 ELEMENTS OF MODERN CHEMIETRY. 

ture and composition of these chlorinated compounds, which 
were discovered Idj V. llegnault. 

C'-^H^Cl ethyl chloride. 

CnVCV^ aichlorethane (ethjlidine chloride)— boils at 57.5°. 

C'^ll^Cl^ trichlorethane— boils at 75°. 

C'^lI^Cl* tetrachlorethane— boils at 127.5°. 

CniCl^ pentachlorethane— boils at 158°. 

C^Cl^ hexachlorethane (scsquichloride of carbon). 

It will be noticed that the second of these compounds is 
isomeric with ethylene chloride, or Dutch liquid, of which the 
description will be found farther on. It may be obtained by 
treating aldehyde with i)hospliorus pentachloride. 

CIP-CHO + PCP = CIP-CIICP + POCP 

Aldehyde. Dichlorethane. Phosphorus oxychloride. 

This mode of formation indicates its constitution, which is 
expressed by the formula 

CIICP 
To distinguish it from its isomeride ethylene chloride, 
CH^Cl 

CH^Cl 
it is named dichlorethane or ethylidene chloride. 

In the scsquichloride of carbon, C'CP, the hydrogen atoms 
are all replaced by chlorine. Carbon scsquichloride is a crys- 
stalline solid, melting at 162°, and boiling at 182° (Faraday). 

ETHYL IODIDE. 

This important compound is prepared by the action of alco- 
hol on iodine in presence of amorphous phosphorus. Phos- 
phorus iodide is formed, and reacts upon the alcohol, yielding 
ethyl iodide and an acid of phosphorus. The former distils 
into the receiver, together with the alcohol which escapes the 
reaction. Water is added, and the lower layer of liquid is 
separated, dried with calcium chloride, and rectified on a water- 
bath. 

Ethyl iodide is a colorless liquid, but becomes brown when 
long kept, especially when exposed to light. Density at 0°, 
1.9753. Boiling-point, 72.2°. 



ETHYL CYANIDE. 4G5 

It can exchange its iodine by double decomposition, as can 
potassium iodide. If ethyl iodide be added to an alcoholic 
solution of silver nitrate, a yellow precipitate of silver iodide 
is at once formed, while ethyl nitrate remains in solution. 

C-H^I 4- AgNO^' = Agl + (eir^)NO^^ 

Ethyl iodide. Silver nitrate. Ethyl nitrate. 

ETHYL CYANIDE. 

C3H5X = CH3-CH2-CN 

This compound is formed when ammonium propionate is 
distilled with phosphoric anhydride. 

(NHO^H^O^ = C^ffN + 2W0 

Ammonium propionate. Ethyl cyanide. 

From this mode of formation, ethyl cyanide is sometimes 
called propionitnlc. The same body exists in the product of 
the distillation of a mixture of potassium cyanide and potassium 
ethylsulphate. 

KCN + ^^^}!>S0* = 5^>S0* + C2IRCN 

Potassium Potassium Potassium Ethyl cyanide, 

cyanide. ethybulphate. sulphate. 

But this product, which is liquid and has a variable boiling- 
point, contains, independently of the true cyanide of ethyl, an 
isomeride of that body, whose existence was foreseen by Meyer 
and discovered by Gautier in the product of the action of 
ethyl iodide on silver cyanide. 

Ethyl cyanide is a colorless liquid having a penetrating and 
pleasant odor. It boils at 96.7° 

When it is boiled with potassium hydrate, potassium propio- 
nate is formed and ammonia is disengaged (Dumas, Malaguti, 
and Le Blanc). 

en^N + KOH + WO = KC^H^O^ + NH^ 

Ethyl cyanide. Potassium propionate. 

When ethyl cyanide is brought into contact with dilute sul- 
phuric acid and zinc, it fixes 4 atoms of hydrogen and is 
converted into propylamine (Mendius). 

C^H^N + H* = C^H^N 

Ethyl cyanide. Propylamine. 

Ethylcarbylamine. — This name was given by Gautier to the 
isomeride of ethyl cyanide already mentioned. It is a color- 
less liquid, having a very penetrating and intensely offensive 
u* 



46G ELEMENTS OP MODERN CHEMISTRY. 

odor. It boils at 79°. With potassium h^'drate it yields po- 
tassium formate and ethylamine. 

r^2Vr55N + K0H + H20-= H — N + KCHO2 

Ethylcarbylamiae. Ethylamine. Potassium 

formate. 

ETHYL NITRITE, OR NITROUS ETHER. 

C^Hs.O-NO 

This compound is obtained by the action of nitric acid on 
alcohol. The reaction is very violent, and abundant red vapors 
are evolved. After passing through a wash-bottle, they are 
conducted into a well- cooled receiver, where the ethyl nitrite 
condenses. 

It is a yellowish, very volatile liquid, whose odor recalls that 
of apples. It boils at 18°. It is but slightly soluble in 
water. Hot water immediately decomposes it into alcohol and 
nitrous acid, the latter being itself decomposed into nitric acid 
and nitrogen dioxide. 



NITRETHANE AND ITS DERIVATIVES. 
C2H5-N02 

This isomeride of ethyl nitrite represents ethane, C-H^, in 
which one atom of hydrogen is replaced by the group (NO')'. 
It is the superior homologue of nitromethane. 

It is obtained, together with a certain quantity of ethyl 
nitrite, when ethyl iodide is treated with silver nitrite. 

C'-'H^I -[- AgNO'' = C-H^'NO^) + Agl 

Etliyl iodide. Silver nitrite. Nitretiiane. 

It is a liquid having a peculiar, ethereal odor and boiling at 
113-114°. Density at 13°, 1.0582 (V. Meyer). 

With nascent hydrogen, it furnishes pure ethylamine. 

C^HXNO^) + 3H2 = C^HXNH'-') + 2W0 

All of the homologues of nitrethane thus yield the corre- 
sponding amines. It is a general character of tlie nifro com- 
pounds, and one which is not possessed by their isomerides, 
the nitrous ethers. In constitution and properties, nitrethane 



ETHYL NITRATE. 46*7 

approaches iiitrobciizol, as will be seen by the following com- 
parison of their forniuho: 

Ethane. Benzol. 

Nitretliano. Nitrobenzol. 

C^H\^H^) C"H'(NirO 

Etliylamine. Phcnylamiiic (aiiilinc). 

The presence of the gi'oup (NO^) confers acid properties 

upon nitrethane. Its sodium compound, C"^H^<;^ , is formed 

either by the action of an alcoholic solution of sodium hydrate 
on nitrethane, or by the direct action of sodium on the same 
body; in the latter case hydrogen is disengaged. Sodium- 
nitrethane is very explosive (V. Meyer and Stuber). 

AVhen it is sought to prepare potassium-nitrethane by the 
action of alcoholic potassium hydrate on nitrethane, the latter 
body is decomposed, yielding, among other products, potassium 
nitrite. Now, the latter salt exerts a remarkable action on ni- 
trethane, giving rise to a new body of complex composition, 
potassium ethyhiitrolate. 

Ethylnitrolic acid may be obtained by a process analogous to 
that which has been described for the preparation of methyl- 
nitrolic acid. Ethylnitrolic acid contains 

C=N.OH 

It crystallizes in light-yellow, transparent prisms, possessing 
a feeble bluish fluorescence and a very sweet taste. It decom- 
poses without violence at 81-82° into nitrogen, nitrous vapors, 
and acetic acid. When boiled with dilute sulphuric acid, it 
decomposes into acetic acid and nitrogen monoxide. 

Ethylnitrolic acid. Acetic acid. 

ETHYL NITRATE, OR NITRIC ETHER. 

(C2H5)N03 

This is obtained by the action of nitric acid upon alcohol in 
presence of a small quantity of urea. The latter body prevents 
the reduction of the nitric acid to nitrous acid. Nitric ether 



468 ELEMENTS OP MODERN CHEMISTRY. 

condenses in the receiver. It is washed with water, dehydrated 
with calcium chloride, and rectified. It is a liquid, having an 
agreeable, ethereal odor. It boils at 86°. Density at (J°, 1.1322. 
Potassium hydrate decomposes it, like all compound ethers, 
forming potassium nitrate and alcohol. 

(C-H^)NO^ + KOH = C-'H^OH + KNO' 

It dissolves in ammonia, especially if the latter be warm, 
yielding ammonium nitrate and ethylamine. The reaction is 
analogous to that of ammonia upon methyl nitrate. 

ETHYL CYANATE. 
C2H=-N=C0 

This compound is prepared by distilling on an oil-bath a 
mixture of 2 parts of potassium ethylsulphate and 1 part of 
recently-prepared and well-dried potassium cyanate. The pro- 
duct which condenses in the receiver is rectified on a water- 
bath (Wurtz). Ethyl cyanate is a colorless liquid, having a 
very irritating odor. It boils at 60°. Potassium hydrate de- 
composes it into carbonic acid gas and ethylamine. It com- 
bines with ammonia, developing heat and producing ethylurea 
(page 443). 

The bodies which have until now been known as cyanic acid 
and ethyl cyanate, are only isomerides of the oxygen com- 
pounds of cyanogen. They should be named isocyanic acid 
and isocyanate of ethyl. The true cyanic ether, (C"-H'.0)CX, 
or rather a polymeride of that body, has been obtained by 
Cloez. It is formed by the action of cyanogen chloride on 
ethylate of sodium. 

CXCl + Xa.OC^ff = CX.OeiP + XaCl 

Cyanogen cliloride. Sodium ethylate. Ethyl cyanate. 

Potassium hydrate decomposes the true ethyl cyanate, like 
all other compound ethers, into alcohol and the corresponding 
potassium salt (cyanate). 

ETHYLSULPHURIC, OR SULPHOYIXIC ACID. 

This body is an example of an acid ether. It results from 
the substitution of a single ethyl group for one atom of hydro- 
gen in sulphuric acid, which is dibasic. 



ii 



ETHYL CARBONATE. 469 

SO* ^ ^>so* 

It is formed by the action of sulphuric acid upon alcohol. 
The mixture of the two bodies becomes hot, and if after cool- 
ing the litjuid be diluted and saturated with barium carbonate, 
anabundant precipitate of barium sulphate will be formed, and 
a soluble salt of barium, the ethylsulphate, will remain in solu- 
tion. A solution of ethvlsulphuric acid may be obtained by 
exactly decomposing this salt with dilute sulphuric acid. 

By boiling, ethylsulphuric acid is decomposed into sulphuric 
acid and alcohol. 

g I feO -t- jj 1 = H j ^ + H p^ 

The ethylsulphates are beautiful salts ; they are crystalliz- 
able and soluble in water. 

Ethyl Sulphate.— ^v^^^I | SO* = c'h^O>^^'- ^^"^ 
body, which represents sulphuric acid in which the two atoms 
of hydrogen are replaced by two ethyl groups, is formed when 
vapor of sulphuric anhydride is passed into ether cooled in a 
freezing mixture (Wetherill). 

(cm^yo -f so^^ = (eH5)2so* 

It is an oily liquid having an acrid taste. Its density is 
1.120. It cannot be distilled. 



ETHYL CARBOXATE. 

Ettling obtained this compound by introducing potassium or 
sodium little by little into ethyl oxalate heated to 130^. The 
metal dissolves, disengaging carbon monoxide. A brown mass 
is obtained, which must be distilled with water. The ethyl car- 
bonate which passes over is dehydrated with calcium chloride 
and distilled. 

It may also be obtained by double decomposition by heating 
ethyl iodide with silver carbonate. 

Ethyl carbonate is a colorless liquid, having a pleasant, ethe- 
real odor ; its density at 0° is 0.9998, and It boils at 125°. 

40 



470 ELEMENTS OP MODERN CHEMISTRY. 

In the cold, ammonia converts it into ctliyl carbamate, or 
urethane. 

C2H5:o>CO + NH3 ^ cnRO>CO + C2H5.0H 
Ethyl curbonute. Ethyl carbamate. 

It yields urea and alcohol when heated to 100° with am- 
monia. 

c'h5:o>CO + 2NH3 _ C0<^'{}2 + 2C2H5.0H 
Ethyl carbonate. Urea. 

ETHYL CHLOROCARBONATE. 

Dumas obtained this ether by passing chlorocarbonic gas 
into alcohol. Water is added to the product of the reaction, 
and the insoluble liquid is separated, dried, and distilled. 

^|>C0 + C2H5.0H = llCl + Qzii?Q>G^ 

Chlorocarbonic gas. Ethyl chlorocarbonate. 

It is a liquid having a pungent, ethereal odor. It boils at 
94°. Hot water decomposes it. Ammonia converts it into 
ethyl carbamate, or urethane. 

C2H5.o>CO + 2Nn3 = NII^Cl + c2ll?J>C0 



SERIES OF SATURATED HYDROCARBONS. 

C2H2n + 2 

To methane and ethane, which have already been described, 
are related numerous hydrocarbons belonging to the same 
series, C"H'^"^"^. They are called saturated because no li^'dro- 
carbons are known in which the number of hydrogen atoms 
exceeds that indicated by the preceding formula. Again, the 
hydrocarbons in question can fix directly no other atoms. For 
example, in order that chlorine can enter into one of their 
molecules, hydrogen must first be removed, and this displace- 
ment is known to take place, atom for atom, according to the 
law of substitution. Thus, if chlorine be made to act upon 
the hydrocarbon (J'W^ (hexane), the compounds ^'H^'Cl, 
CH^'^CF, CH'^CP, maybe obtained successively. Let us con- 
sider the first of these compounds, C^tF'Cl. The CI may be 
replaced by the group OH, and the chloride is thus converted 



SATURATED HYDROCARBONS. 471 

into an alcohol. For this purpose the chloride is caused to 
react with a silver salt, the acetate, for example, and hexyl 
acetate is formed by double decomposition. 
CH^^Cl 4- Ao-eH^O- = C^H^ie^H^O' + AgCl 

Hexlyl chloride. Silver acetate. Hexyl acetate. 

Boiling potassium hydrate will transform this ether into 
hex^'l hydrate. 
CTI^IC-'H^O^ + KOH = KC^H^O^ + C^H^IOH 

Hexyl acetate. Potassium acetate. Hexyl liydiate. 

This series of reactions permits of the successive transforma- 
tion of any hydrocarbon of the saturated series into a chloride, 
an acetate, and a hydrate, and the latter is the alcohol corre- 
sponding to the hydrocarbon. The following is the series of 
saturated hydrocarbons : 



CH* 


methane. 


C2H6 


ethane. 


C3H8 


propane. 


C4H10 


butanes. 


C5H12 


pentanes. 


CCRU 


hexanes. 


C7II16 


heptanes. 


c^w^ 


octanes. 



C9fi20 nonanes. 
C10H22 decanes, etc. . 

All of these hydrocarbons, after the fourth of the series, up 
to the term C^^H^*, have been obtained from petroleum and 
the products of distillation of bitumen and peat. Towards 
the close of the distillation, when the temperature passes above 
300°, the products which distil condense to a solid mass on 
cooling. When properly purified, this solid forms a colorless, 
translucent mass, which has received the name paraffin. It 
is probably a mixture of several hydrocarbons of the series 
(^njj2n+2 j|.g point of fusion varies between 45 and (J5°. 

All of the compounds belonging to this series cannot be 
described here, but we may briefly consider their constitution. 

The third member of the series, propane, C'^H®, has the con- 
stitution indicated by the formula CH'-CH'-^-CH^ It is a gas 
which liquefies at — 17°. 

Its superior homologue, butane, C*H^°, has the constitution 
CH^-CH^-CH'^-CH^ and can be obtained by the action of 
zinc or sodium on ethyl iodide. 

2C^H^I -f Na^ = 2NaI -|- C^H'^ 

It is a colorless gas, condensable at -|-1°. But we have 



472 ELEMENTS OF MODERN CHEMISTRY. 

here a remarkable instance of isomerism. There is another 
butane, isomeric with the preceding, and having the consti- 

CFP 

tution expressed by the formula CIF-CII<pTT3. It is tri- 

methyl-mothane, CH(CH"^)^, while normal butane is dimethyl- 
ethane, C'H*(CH^;^ or propyl-methane, CH^(O'H^). The sig- 
nification of these words and formulae is evident. Trimethyl- 
methane is methane, CH*, in which three atoms of hydrogen 
are replaced by three methyl groups. The difference in the 
atomic grouping is attended by a difference in properties. 
Trimethyl-methane is a gas which condenses only at — 17°. 

The succeeding terms of the series present isomerisms of 
the same kind, but much more numerous as their molecular 
complication is greater. They need not be described here, since 
the same general principles apply to all. 

SERIES OF ALCOHOLS. 

Ethyl alcohol, of wdiich the more important compounds 
have been briefly described, is not the only product of the fer- 
mentation of saccharine liquids. Other alcohols are formed in 
small quantity in this reaction, which is conducted on an exten- 
sive scale in the arts. Among these alcohols of fermentation 
are the following : 

Propyl alcohol, or propyl hydrate, C^H^.OH 
Butyl alcohol, or butyl hydrate, C*IP.OH 
Amyl alcohol, or ainyl hydrate, C^IPi.OH 
He.xyl alcohol, or hexyl hydrate, C^Hi-'.OH 
Heptyl alcohol, or heptyl hydrate, CMP^GH 

To each of these alcohols correspond numerous ethereal com- 
pounds in which the groups propyl, O'H', butyl, C*H', amyl, 
C^H^\ etc., are substituted for the hydrogen of the hydi-acids 
and oxacids. To each of these alcohols correspond also an 
aldehyde and an acid, just as ordinary aldehyde and acetic acid 
correspond to ordinary alcohol or ethyl hydrate. 



CH3 


CH3 


CH3 


CI12.0H 

Alcohol. 
CH2-CII3 


CHO 

Aldehyde. 

CH2-CH3 


CO.OH 

Acetic acid. 

cn2-cH3 


CH2.0H 

Propyl alcohol. 


CHO 

Tropyl aldehyde. 

C3H7 


CO.OH 
Propionic acid. 
C3H7 


CH20H 
Butyl alcohol. 


CHO 
Butyric aldeliyde. 


CO.OH 

Butyric ncid. 



SERIES OF ALCOHOLS. 473 

All of these alcohols contain a group CH'.OH united to a 
group or radical, C"H"""^^ When they are converted }>y oxi- 
dation into aldehydes and acids, the group CH-'.Oli is trans- 
formed into a group CHO, characteristic of the aldehydes, or 
a group CO. OH, characteristic of the acids. These alcohols 
are said to be ^;?7"y;i6?r^. Beginning with butyl alcohol, the 
primary alcohols may have several isomeric modifications, as 
Avill be seen shortly. Independently of the primary alcohols, 
there are others, isomeric with the preceding, but distinguished 
from them by the fact that they do not yield corresponding 
aldehydes and acids when oxidized. These iso-ahohols are 
divided into secondary^ which contain the group CH.OH, and 
tertiary, which contain the group C.OH (Kolbe). Without 
entering into the details of this subject, we may cite two 
examples : 

1. By the action of nascent hydrogen upon acetone, Friedel 
obtained isopropyl alcohol. 

CH3 CH3 

CO + m = cii.oH 

CH3 CH3 

Acetone. Isopropyl alcohol. 

By oxidation of this iso-alcohol, which is a secondary alcohol 
(containing the group CH.OH), acetone is again reproduced. 

CH3 CH3 

CH.OH + = H20 + CO 
CH3 CH3 

2. Boutlerow discovered an isomeride of butyl alcohol, and 
named it tertiary butyl alcohol; its constitution is expressed by 
the formula 

CH3 
CH3-C.0H 
CH3 

This alcohol contains, as is seen, the group C.OH. It yields 
neither aldehyde nor acid by oxidation. 

In the primary alcohols, the OH is united to a C which is 
combined with only one other carbon atom ; in the secondary?- 
alcohols, to a C united to two other carbon atoms ; while in the 
tertiary alcohols, the C to which the hydroxyl is attached is 
joined to three other atoms of carbon. 

40- 



474 ELEMENTS OP MODERN CHEMISTRY. 

Propyl Alcohol, C^'H^O = Cir^-CH^-CH^OH.— This was 

discovered by Cliancel in the oily liquid remaiiiiiiii; after the dis- 
tillation of brandy. It is a spirituous liquid, boiling at 98°. 
Its iodide, C^H^I, boils at 104.5° (I. Pierre and Puchot). 

The iaopropyl alcohol of Friedel is formed under the circum- 
stances just indicated. Its constitution is expressed by the 
formula 

CH^-CH.OH-CH^ 

It boils at 86°. When propylene gas is heated with hydri- 
bodic acid, isopropyl iodide, C'H^I, is obtained, boiling at 92°. 

C^H« + HI = O^H^I 

Propylene. Isopropyl iodide. 

Silva has described numerous derivatives of isopropyl alco- 
hol. 

Butyl Alcohols, C^H^^O.— The constitution of the butyl 
alcohol of fermentation, which is a primary alcohol, is expressed 

by the formula ^|J3>CH-CH10H. It is isobutyl alcohol. 

In 1852, Wurtz obtained it from the fusel-oil from the rec- 
tification of beet-root alcohol. It is a colorless liquid, having 
a penetrating odor analogous to that of amyl alcohol, but more 
spirituous. It dissolves in 10.5 times its volume of water. It 
boils at 109°, and yields on oxidation an acid isomeric with 
butyric acid and called isohntyvic. 

It may be regarded as ordinary alcohol in which two atoms 

of hydrogen are replaced by two methyl groups. 

CH3 cn(CH3)2 

CH2.0H CH2.0H 

Alcohol. Isobutyl alcohol. 

Lieben discovered normal hiityl alcohol, isomeric with the 
alcohol of fermentation, and which yields butyric aldehyde and 
butyric acid by oxidation. He obtained this alcohol by the 
action of sodium amalgam in presence of water on butyral 
(butyric aldehyde). 

f "' + m = f "' 

CHO CH2.0TI 

Butyral. Normal butyl alcohol. 

De Luynes obtained another isomeride of butyl alcohol by 
the reduction of erythrite (page 505). This akoliol is second- 
ary, having the constitution CH'^-Cir'-CH(OH)-CHl It 



SERIES OF ALCOHOLS. 475 

boils at 116.9° (Liebcn). The corresponding iodide, CTP- 
CH--CHI-CH^ boils at 118°. It is formed by the following 
reaction : 
C*H»»0* + 7HI = C*H«I + 4H^0 + 3F 

Erythrite. Secondary butyl iodide. 

The tertiary butyl alcohol discovered by Boiitlerow has re- 
ceived the name trimethi/lcarhuiol^ on account of its constitu- 
tion, which has already been indicated. It is a well-crystallized 
compound, melting between 20 and 25°. 

In conclusion, four alcohols are known having the composi- 
tion C*H^°0, and presenting a remarkable instance of isomer- 
ism. Their constitutions are again indicated in the following 
formulae : 



CIP 


CH3 


CH3 


CIP 


CH2 


CH3-CH 


CH2 


CH3-C.0H 


CH2 


CH2.0H 


CH.OH 


CH3 


CH2.0H 

Normal primary 

butyl alcohol. 

(Lieben.) 


Primary isobutyl 

alcohol • t'eriiieiitation). 

(AViutz.) 


CIP 
Secondary butyl 
alcohol. 
CDe Liiyiu'S.) 


Tertiary butyl 

alcoliol. 

(Boutlerow.) 



pTT3 

Amyl Alcohol of Fermentation.— en^^O = CH3>CH- 

CH'^-CHIOH, This is the most abundant constituent of 
fusel-oil from beet-root and potatoes, as well as of that from 
the marc of grapes, from whiskey, etc. These products are 
only the residues of the distillation of alcohol from various 
sources. 

Amyl alcohol is a colorless liquid, having a rather unpleasant 
odor. It boils at 132°. Its density at 15° is 0.8184. It is 
nearly insoluble in water. It turns the plane of polarization 
to the left. There is, nevertheless, an amyl alcohol which has 
no action upon polarized light, and which Pasteur has named 
inactive amyl alcohol. The latter boils at 130°. It is iso- 
meric with the amyl alcohol of fermentation, from which it 
differs in physical properties, but presents the same composi- 
tion and the same chemical properties. It is a case of lohysical 
isomerism. 

When submitted to the action of zinc chloride, amyl alcohol 
is converted into amylene and polymerides of that body (di- 
amylene, C^'^H^", triamylene, C^'H''"). 

Amyl alcohol. Amylene. 



4V0 ELEMENTS OP MODERN CHEMISTRY. " 

By oxidation, amyl alcohol yields valeric aldehyde and val- 
eric acid. 

C^H^^Q 4_ = H-'O + C^H'OO 

Valeral, or valeric aldehyde. 

C^H^^O + 0" = ir^O + C^H'W 

Valeric acid. 

The numerous amylic ethers cannot be described here. 

Amijl oxide, (C^IP^)-'O, is a colorless liquid, having a suave 
odor, and boiling at 1TG° (Williamson). 

Amyl chloride, C^H^^Cl, is a colorless liquid of an aromatic 
odor, boiling at 102°. 

Amyl iodide, C^H"!, is a colorless liquid, which becomes 
brown when exposed to the light. Density at 0°, l.-4()76. 
Boiling-point, 147°. 

Isomerides of Amyl Alcohol. — At least five alcohols are 
known havinii' the composition of amyl alcohol. Independ- 
ently of the" normal alcohol CH^-CH-'-CH-CH^-CH-'.OH 
(boiling-point, 137°), which Lieben obtained by the action of 
nascent hydrogen on valeral (valeric aldehyde), and the alco- 
hol of fermentation which has just been described, and which 
may be called isopropyl-ethyl alcohol, 

CW^ CI12.0 

there are three others having the composition C^H^'O. The 
most important is the compound which is generally called hy- 
drate of amylene, because it breaks up very readily into water 
and amylene. It is a tertiary alcohol of the form 

^{{3>C.OH-CII-'-CII3 

Its corresponding iodide is formed by direct unicm of hydri- 
odic acid and the amylene prepared by the action of zinc 
chloride upon amyl alcohol of fermentation (A. Wurtz). 

CH^" + HI = C^H"I 

This iodide boils at 129°. B}- treating it with water and 
silver oxide, Wurtz obtained the alcohol which he named 
hydrate of amylene. The latter liquid boils at 105°. It is 
decomposed by heat alone into amylene and water, according 
to the equation before given. The other isomerides of amyl 
alcohol need not be described. 



SERIES OF ALCOHOLS. 477 

Hexyl and Heptyl Alcohols. — Faget announced tliat the 
residues from the distillation of fusel-oil from fermented uTai)e- 
juiee contained a small quantity oi' hcxj/l (CII'^O) and /ir])f^l 
(C'ir*'0) alcohols, but such alcohols have not been rcfound 
in that product. 

Normal hexyl alcohol has been obtained from the volatile 
oil of the seeds of lleraclrum giganteum., an oil which contains 
butvrate of hexyl, eH^^C'H'O^ The normal alcohol boils 
at 157-158°. 

Normal heptyl alcohol, C^H^'^0, has been prepared by the 
action of nascent hydroiicn on oenanthic aldehyde C'lF^O. 
It boils at 175-177°, and has an aromatic odor. 

Octyl Alcohols, C^H^^O. — Normal octyl alcohol may be ex- 
tracted from the seeds of Ileracleum spomli/Uum and Ilera- 
clcum fftgauteiim, in which oct}'! acetate, C^IP'.C-^H'^O'^, exists. 
This ether is separated and decomposed by boiling potassium 
hydrate. Its boiling-point is between 190 and 192°. 

Bonis discovered secondary octyl alcohol. By boiling one 
of the acids produced by the saponification of castor-oil, rici- 
nolic acid, with potassium hydrate. Bonis decomposed it into 
sebacic acid and a new secondary alcohol. This is octyl alco- 
hol, C^H^^O, a colorless licjuid having a pleasant, aromatic odor, 
and boiling at 178°. The following equation explains its 
formation : 

Kicinolic acid. Potafssium sebate. Octyl hydrate. 

Cetyl Alcohol. — The concrete portion of an oil which fills 
the cranial sinuses of the sperm-whale is called spermaceti. 
When properly purified it occurs in beautiful pearly plates, 
fusible at 49°. It is a compound ether of which the nature 
was recognized by Chevreul in 1823. By submitting it to the 
action of potassium hydrate, that chemist decomposed it into 
palmitic acid and a new alcohol which he called efhcd, to denote 
its relations with alcohol and ether. It is now called cef?/l 
alcohol, or ccf?/l hydrate. 

^C1^hS>^ + ^^H = C16II33.0H + KC16H'^102 
Cetyl palmitate. Cetyl hydrate. Potassium palmitate. 

It belongs to the same homologous series as the preceding- 
alcohols. 

Alcohols from Wax. — The most complex alcohols of the 
series under consideration were obtained from wax by Brodie. 



4<8 ELEMENTS OF MODERN CHEMISTRY. 

Ordinary beeswax is a mixture of a fatty acid, C'''n^^O^ called 
cerotic acid (cerin), and a compound ether, i\\Q palniitdte of 
myricyl (myricin). The two bodies are separated by alcohol, 
which readily dissolves the first, but in which the second is but 
slightly soluble. By boiling the palmitate of myricyl with 
potassium hydrate, it breaks up into palmitic acid and hydrate 
of myricyl, or myricyl alcohol, C'^H'^^'O. 

Chinese icax is a compound ether ; it is cerotate of ceryl, and 
may be decomposed by caustic potassa into cerotic acid and 
ceryl hydrate, or ceryl alcohol, C'^H'^O. The hydrates of cetyl 
and ceryl are solid bodies. 

ALLYL ALCOHOL. 

C3H5.0H = CH2^CH-CH2.0H 
All of the alcohols thus far considered belong to the series 
C"H'-"+'0. There are other monatomic alcohols which belong 
to different series, that is, in which there are different relations 
between the number of hydrogen atoms and the number of 
carbon atoms. Among these other alcohols, the most impor- 
tant is allyl alcohol, or hydrate of allyl, so named because it is 
closely related to the essential oil of garlic, which is allyl sul- 
phide. Another natural oil, that of mustard, is sulphocyanate 
of allyl. 

C^H^OH (C^H°)^S C^H^CXS 

Allyl hydrate. Allyl sulphide. Allyl suliihocj-anate. 

Hofmann and Cahours prepared allyl hydrate and a great 
number of its derivatives artificially by the aid of allyl iodide, 
O'H'I, which is formed when glycerin is acted upon by iodide 
of phosphorus, P-P (Berthelot and de Luca). This iodide, 
whose relations to allyl alcohol are the same as those of ethyl 
iodide to ordinary alcohol, is a colorless liquid, having a slightly 
pungent, garlicky odor, and boiling at 101°. 

AVhen heated with mercury and concentrated hydrochloric 
acid, it yields pure propylene gas (Berthelot). 

1^^W\ + 2IIC1 + 4Hg = 2C^ir' + Hg^P + Ilg-CP 

Allyl iodide. Propylene. 

Tollens and Henninger discovered a very simple process for 
the preparation of allyl alcohol. It consists in heating formic 
acid, or oxalic acid, from which the former acid is produced, 
with glycerin to 220°. The allyl alcohol which distils is 



COMPOUND AMMONIAS. 



479 



washed with a concentrated sohition of potassium carbonate, 
and rectified over lime. In this reaction, a monoformine of 
glycerin is first produced, and this decomposes at 220° into 
carbon dioxide, water, and allyl alcohol. 



ro.ciio 

C3H5^0II = 

(oh 

Monoformine of glycerin. 



C02 



IPO 



Cnis.OII 
Allyl alcohol. 



It will be seen that the reaction is really a reduction. 

Allyl alcohol is a colorless liquid, boiling at 97°, and having 
a pungent, alcoholic odor. It dissolves in all proportions of 
water. Density at 13°, 0.86. 

Allyl alcohol is an unsaturated compound ; it can fix directly 
two atoms of hydrogen, chlorine, or bromine, or one molecule 
of hydrobromic acid, etc. 

Acrolein, a volatile liquid that is formed in the distillation 
of fatty bodies, is the aldehyde of allyl alcohol. Acrylic acid 
is the corresponding acid. 



COMPOUND AMMONIAS, OE AMINES. 

Wurtz gave these names to the basic combinations resulting 
from the substitution of alcoholic radicals, such as methyl, 
ethyl, etc., for the hydrogen of ammonia. This substitution 
may be more or less complete ; 1, 2, or 3 atoms of hydrogen 
may be replaced by as many alcoholic groups. Hence there 
are various classes of amines ; they are designated by the names 
primary, secondary, and tertiary. 





PRIMARY AMINES. 


SECONDARY AMINES. 


TERTIARY AMINES 


H) 


CH3) 


cn^ V 


cH-n 


hIn 


H In 


CH3 In 


CH3 I N 


Hi 


Hj 


hJ 


CH3j 


Ammonia. 


Methylamlne. 


Dimethylamine. 


Trimethylamine. 




C2H5^ 


C2H5 ) 
C2I15 ' N 
Hj 


C2II5 ) 




H In 


C2H5 [ N 




HJ 


CfHsj 




Ethylamine. 


Diethylamine. 


Triethylamine. 



Lastly, bases are known which are the most energetic of 
all. and may be considered as derived from the hypothetical 
hydrate of ammonium by the substitution of alcoholic radicals 
for 4 atoms of hydrogen. 



480 ELEMENTS OF MODERN CHEMISTRY. 

II 1 C2H5 ] 

H J C^lis J 

Ammonium hydrate. Hydrate of tetrethylammoninm. 

The latter ammoniated bases, as well as the secondary and 
tertiary amines, were discovered by Hofmann. 

In the amines, nitrogen acts as a triatomic element or tri- 
valent; but it may assume two other atomicities. In sal- 
ammoniac, it is pentatomic, and it may play precisely the same 
part in the amines. 







CI 


(Oil)' 


H 


cms 


II H 


(C2H5)' (C2H5)' 


1 


1 


\ / 


"-^ ^/ 


N 


N 


N 


N 


/\ 


/\ 


/\ 


/\ 


H H , 


C2H5 C2H5 


H II 


(C2H5)' (C2II5)' 


Ammonia. 


Triethylaniine. 


Ammonium 


Tetrethylammonium 






cliloride. 


hydrate. 



Related to the amines are various organic combinations 
which have the same constitution, but in which the nitrogen 
is replaced by an analogous element, such as phosphorus, 
arsenic, or antimony. A great number of these bodies have 
been discovered, of which the more important are 

C2II5 ) C2H5 ) C2II5 ) 

C2I15 L p'/' C2H5 [ As'" C2II5 I Sb 

C2II5 ) C2H5 j C2H5 j 

Triethylphosphine. Tiiethylarsine. Triethylstibine. 

The nitrogenized bases that have just been considered belong 
either to the type NX^ or to the type NX^. A new class of 
compounds has recently been discovered, belonging to the type 
N^X*. 

It is evident that the group NX^ (amidogen) cannot exist 
in the free state. If it could be isolated, it would probably 
combine with itself, forming a double molecule 

Fischer has made known several substituted derivatives of 
this body, N-H*, which he names hi/drazinc He has described 
etlujlhydrazhie^ NH^-NH(C-H^). It is a base soluble in 
water, and having an ammoniacal odor ; its hydrochloride con- 
tains N^IP(C-'IP).2HC1. 

The compound ammonias cannot all be described here ; we 
need only consider the more important. 



METUYLAMINE. 481 



METHYLAMINE. 

CH3) 
CH^N = H I N 

hJ 

This body may be prepared by boiling together potassium 
hydrate and metliyl eyanate or cyanurate, and passing the 
vapors which are disengaged into dilute hydrochloric acid; 
methylamine hydrochloride is thus formed. 

Cii3/^ + 2K0H = K2C0'5 + HVN 
Methyl cyanato. Methylamine. 

The solution is evaporated to dryness, and the residue fused 
and allowed to cool ; it is then mixed with double its weight 
of powdered quick-lime, and the mixture gently heated. The 
methylamine disengaged may be collected over mercury. 

It is a colorless gas, which condenses to a light liquid at a 
temperature a few degrees below 0°. It is inflammable, and 
burns with a pale flame. Its odor is strongly ammoniacal and, 
at the same time, recalls that of the sea. It is the most solu- 
ble of all gases. 1 volume of water at 12.5° absorbs 1153 
volumes of methylamine. The aqueous solution possesses the 
odor of the gas, a caustic taste, and a strong, alkaline reaction. 
Like ammonia, it precipitates the oxides from solutions of the 
metallic salts. 

If a solution of methylamine be added to a solution of cupric 
sulphate, a light-blue precipitate is first formed, but disappears 
if an excess of methylamine be added, yielding a beautiful blue 
solution. 

Methylamine Hydrochloride, CH^N.HCl, diff"ers from am- 
monium chloride by its solubility in boiling alcohol, from which 
it is deposited on cooling in large, colorless, deliquescent plates. 
With platinic chloride it forms a yellow precipitate, soluble in 
boiling water, from which it crystallizes in golden-yellow scales. 

It is a chlaroplatinate, (CH^N.HCOlPtCP. 

DIxMETHYLAMINE, TRIMETHYLAMINE, TETEA- 
METHYLAMMOxXIUM HYDRATE. 

These compounds were discovered by Hofmann. 
Dimethylamine^ (CH^j^NII, is a combustible gas which lique- 
fies at 8°. 

V 41 



482 ELEMENTS OF MODERN CHEMISTRY. 

Trimefhylamine^ (CH'')^N, exists ready formed in the Clieno- 
jxjdium vulvcn-ia, in the flowers of Cratscgus oxyacantha^ in 
herring-brine, in eod-Uver oil, and in coal-gas tar. Vincent 
extracts large quatities of it from the residues of the distilla- 
tion of fermented beet-juice. 

At ordinary temperatures it is a gas; it liquefies at 9°. It is 
very soluble in water and in alcohol. It has a strong, ammoniacal 
odor, and an intense, alkaline reaction. It unites directly with 
methyl iodide, forming the iodide of tetramethylammonium. 

(CIPj'N + CIFI ^ (CIFj'^^I 
This iodide possesses all the appearances of a salt. It is 
soluble in water, and the solution treated with silver oxide yields 
silver iodide and tetramethylammonium hydrate. 

2(CIPyNI -f Ag^O -f H'^O = 2AgI -f- 2(CH^)*N.0H 
The latter body is very soluble in water, and the solution is 
caustic. When submitted to dry distillation, it decomposes into 
trimethylamine and methyl alcohol. 

(CH=')^N.OH = CHIOH + (Cff)'N 

ETHYLAMINE. 



S" = HJN 

hJ 



Ethylamine is prepared by a process analogous to that which 
yields methylamine ; cyanate or cyanurate of ethyl is decom- 
posed with boiling potassium hydrate, and the vapors arc con- 
densed in very dilute hydrochloric acid. The dry ethylamine 
hj^drochloride is then treated with quick-lime (A. Wurtz). 

Another process has been indicated by Hofmann. It consists 
in causing ammonia to react upon the bromide or iodide of 
ethyl. 

C2mBr + H I N = H ^ N.HBr 

iij hJ 

Ethylamine hydrobromide. 

Ethylamine is a light, mobile, colorless liquid; it boils at 
18.7°. Its odor is strong and exactly resembles that of am- 
monia. 

Ethylamine is inflammable. It mixes with water, alcohol, 
and ether in all proportions. Its a(pieous 'solution is caustic, 
and precipitates most of the metallic salts like solution of am- 



ETHYLPHOSPHINES. 483 

monia, and, like the latter, redissolves cupric hydrate, forming 
a blue li((uid. 

Ethylamine Hydrochloride, C^H^N.HCl.— This salt crys- 
tallizes in large, deliquescent plates, soluble in absolute alcohol. 
Its aqueous solution yields with platinic chloride a precipitate 
composed of 3'ellow scales, soluble in boiling water, and consti- 
tuting a chloro-platinate, (C''H'N.HCl)'-.PtCh 

DIETHYLAMINE, TRIETHYLAMINE, TETRETHYL- 
AiAlMONIUM HYDRATE. 

Diethylamine, C^H^ v N, was obtained by Hofmann by heat- 
ing ethylamine with ethylbromide, and decomposing the die- 
thylamine hydrobromide formed by an alkali. 

C2H5) C2I15) 

H y N + C2H6Br = Cm^ I N.IIBr 

hJ hJ 

Ethylamine. Diethylamine hydrobromide. 

The free base is a liquid having an ammoniacal odor and 
boiling at 57.5° 

Triethylamine may be formed by the action of ethyl bro- 
mide on diethylamine ; triethylamine hydrobromide is formed, 

Q2j^b [ ^Jl^r, from which alkalies cause the disengagement 

of triethylamine, a colorless liquid, boiling at 91° ; its odor 
is ammoniacal and its reaction strongly alkaline. 

Tetrethylammonium Hydrate. — When a mixture of ethyl 
iodide and triethylamine is heated on a water-bath, the two 
bodies combine, forming the compound which Hofmann has 
named tetrethylammonium iodide. 

Q'Wl •+ (C'H^y^N = (C^H5)^N.I 

Ethyl iodide. Triethylamine. Tetrethylammonium iodide. 

When this is treated with silver oxide and water, it yields 
silver iodide and tetrethylammonium hydrate, (C^H^)*N.OH, a 
powerful base, which is crystallizable and soluble in water. Its 
energy is comparable to that of potassium hydrate. 

ETHYLPHOSPHINES. 

Primary, secondary, and tertiary ethylphosphines are known, 
as well as the compounds of tetrethylphosphonium. 



484 ELEMENTS OF MODERN CHEMISTRY. 

c^ipl cni^) C^HM ^^^^ 



11^ 






Etliylphosphine. Dicthyli)hosi)liinc. Triotliylpliosphiiic. Tetretliylphusplioniiim. 
(i*rimiiry.) (yecoiidiiry.) (Tcrtiiir.v.) 

The first two have been recently discovered by Hofnuinn. The 
third is due to an admirable research of Ilof'niann and C/ahours, 
who obtained it by the action of phosphorus trichloride on zinc 
ethyl. 
2P0P + 3[Zn(eiP)'^] = 2[P(C-'IP)''] -f 3ZnCP 

Zinc ethyl. Triotliylplio.sphine. 

The operation must be conducted out of contact with the 
air, and the zinc ethyl must be diluted with anhydrous ether. 

JMoni'thylphosphine and diethyli)hosphine are produced when 
ethyl iodide is made to react uj)on j)liosphonium iodide, PlIM, 
hydriodide of hydrogen phosphide (page 11)7), in presence of 
an excess of zinc oxide. 

2CfII5I + 2PIHr + ZnO = 2[{CnP)ll^P.Ul] + ZnI2 + H20 

2cnr^i + vwi -f- ZnO = {cm^ym^. ni + ZnP + ir^o 

As both reactions arc accomplished simultaneously, both 
phosphines are obtained at the same time. They are separated 
by the action of watiu- upon the two h^nlriodides which arc 
formed. That of monethylphosphine is decomposed by water, 
while that of diethylphosphine is oidy decomposed by the alka- 
lies. It is sufiicicut then to add water to the ]>roduct of the 
reaction in order to set free the nionethyl})hosphine ; when 
tlie latter has been completely expelled by heat, potassium hy- 
drate added to the residue will cause the disengagement of the 
diethylphosphine. These operations should be conducted in a 
current of hydrogen. 

Monethylphosphine, (C-fP)H'P. — This is a colorless liquid, 
lighter than water, in which it is insoluble, and boiling at 25°. 
It has a most disagreeable odor. It takes fire on contact with 
chlorine or nitric acid. Its hydriodide crystallizes in beautiful, 
white, ((uadrangular tables. 

Diethylphosphine, (C*IP)*''riP. — A colorless liquid, lighter 
than water, anil boiling at 85°. It is very avid of oxygen, and 
sometimes takes lire spontaneously on contact with the air. 

Triethylphosphine, (C-I1'')''P. — This is a colorless liquid, 
boiling at 127.5^. Density at 15°, 0.812. It combines di- 
rectly with oxygen, forming fritfhf/fp/iospJu'iie (/xuh% (O'll'O'PO. 
The latter is a crystalline solid, very soluble in water and in 
alcohol. It distils at 240°. 



PRODUCTS OF OXIDATION OF ETIIYLIMIOSPIIINES. 485 

"Wlicn treated witli etliyl iodide, triethylpli()S|)liine yields 
totretliyli)li()S|)lK)nium iodide, (Cni*)'*PI, a compound wliich 
may be obtained in beautiful crystals. When this iodide is 
acted upon by moist silver oxide, it furnishes the corresponding 
hydrate, which is an energetic base. 



2[(C^IP)n*I] + Ag-O 

Tftreili3li)liosi)houiuia 
iudidf. 



2AgI + 2[(C^IP)'P.0II] 

Totiethyll'lK'Mplioniuiii 
lijdrato. 



PRODUCTS OF OXIDATION OF ETIIYLPIIOS- 
PHliNES. 



"When the ethylphosphines are treated with fuming nitric 
acid under suitable conditions, they act in a characteristic man- 
ner. Monethyl])hosphine is transformed into a dibasic acid, 
moiictliylpJioaplil uic ; diethylj)hosphine yields a monobasic acid, 
dlctJijjlj)hoi>j)lLuiic. Triethylphosphine yields an indifferent 
oxide, which has already been mentioned. Now, if it be remem- 
bered that under the same circumstances hydrogen phosj)hide 
furnishes phosj)horic acid, it will be seen that the preceding 
oxidation compounds may be regarded as phosphoric acid, in 
which 1, 2, or 3 groups Oil are replaced by as many ethyl 
groups. 



fH 


roil 


P^ H 


po^ on 


(II 


(on 


Hydrogen phosphide. 


Phosphoric acid. 


V\ II 


PO-^ oil 
[oh 


In 


Monetliylphosphino. 


Monethylpho8i)iiinic acid. 


(•I 


( nil'"' 
PO \ C'^115 


1 OH 


Diethylphosphine. 


Dielhylphospliinic acid. 


f C2H5 


f C'^IP 


P \ C2H5 


po-^ c:m^ 


(ynv> 


[v;nv^ 


Triethylphosphine. 


Triothyli»hosphine oxide. 



The compounds of arsenic and ethyl are entirely analogous 
to the phosphines; they have already been alluded to. Besides 
these, there are ethylic combinations corresponding to cacodyl 
and its derivatives. 

41* 



480 ELEMENTS OF MODERN CHEMISTRY. 

ORGANO-METALLIC COMPOUNDS. 



ZINC-ETHYL. 

One of the more important of the compounds formed by the 
union of the metals with alcohoHc radicals is zinc-ethyl, dis- 
covered by Frankland. 

It is prepared by heating ethyl iodide with zinc-turnings 
and a small quantity of sodium on a water-bath. Zinc iodide 
and zinc-ethyl are formed. When the reaction is terminated, 
the product is distilled and that portion collected which passes 
above 115°. 

Zinc-ethyl is a colorless, mobile, and highly-refractive liquid. 
It has a peculiar, penetrating, and very disagreeable odor. It 
boils at 118°, It takes fire spontaneously on contact with the 
air, burning with a green flame, and producing white fumes 
of zinc oxide. 

If water be added to a small quantity of zinc-ethyl contained 
in a tube, a brisk eifervescence at once takes place, and a white 
deposit is formed. The gas is ethane, and the deposit is zinc 
hydrate. 

Zn(C^H=)'^ + 2IP0 = Zn(OH)^ -[- 2C'^H« 

Zinc-ethyl will enter into double decompositions. 

By the action of phosphorus trichloride on this body, Hof- 
mann and Cahours obtained tricthylphosphine and zinc chloride. 

There is a zinc-7neth?/l, Zn(^CH^)'^, corresponding to zinc- 
ethyl. 

MERCUR-METHYL AND MERCUR-ETHYL. 

These compounds were obtained by Frankland and Duppa, 
by the action of methyl and ethyl iodides on sodium amalgam 
(sodium 1, mercury 500), in presence of a small quantity of 
acetic ether. 

Merciir-ethyl is a colorless, inflammable liquid, insoluble in 
water. Density, 2.44. Boiling-point, 158-100°. It is one 
of the most dangerous bodies knoAvn. The inhalation of its 
vapor for any length of time, even in small quantity, will 
produce fatal poisoning. 



STANNETHYLS. 487 

Chlorine, bromine, and iodine instantly decompose mercur- 
ethyl with formation of a compound of niercur-monethyl. 

Mercur-etliyl. Ethyl iodide. Mercui-niouethji iodide. 

STANNETHYLS. 

The discovery of the numerous compounds of tin and ethyl 
is due to Lliwig. Their history has been completed by Frank- 
land, Cahours, and lliche. 

As the nomenclature and constitution of the stannethyls 
have already been indicated (page 424), we need only consider 
a few of these interesting compounds. 

Stannodiethyl, Sn(C'"H^)^— The iodide of this compound 
is obtained when ethyl iodide is heated with tin-filings to about 
180^. This iodide, Sn(C'tP)'P, purified by crystallization in 
alcohol, furnishes free stannodiethyl when its solution is treated 
with zinc, which removes the iodine. 

Stannodiethyl is an oily, yellow liquid, which does not vola- 
tiliz3 without decomposition. When heated to 150° it begins 
to boil, but the greater part of it is decomposed into stanno- 
tetrethyl and tin. 

2[Sn(C^ff)T = Sn(C^HO* + Sn 

The iodide of stannodiethyl crystallizes in pale yellow needles. 
In its solution, the alkalies precipitate the oxide Sn(C'^H^)''^0, 
which forms an amorphous, white precipitate, insoluble in water 
and alcohol, but soluble in the alkalies and acids with which it 
forms salts. 

Stannotriethyl or Sesquistannethyl, Sn\^C'H5)« = (C'Wy 
Sn-Sn(C'■^H^j■^ — This is formed, together with the preceding 
compound, by the reaction of ethyl iodide on an alloy of tin and 
sodium. It is separated by fractional distillation ; it boils between 
265 and 270°. It plays the part of a radical and combines 
directly with oxygen. The oxide contains Sn^(C^H^)'*0 = 
[Sn(C^H^)'']^0. It combines with the elements of water, form- 
ing a hydrate, Sn(C"'^H^)\OH, crystallizable in prisms. These 
crystals are fusible at 44°. The oxide distils at 272°. It 
reacts with the acids to form crystallizable salts. 

[Sn(eH5)3]20 + 2IIN0' = 2[Sn(eH5)lNO-'] + H'^0 

Stannotriethyl oxide. Stannotriethyl nitrate. 



488 ELEMENTS OF MODERN CHEMISTRY. 

The iodide, Sn(C'^H^)^I, is a liquid having a mustard-like 
odor, and distilling without decomposition towards 235-238°. 
Density at 15°, l!833. 

Stannotetrethyl, Sn(C^H^)^ — Colorless liquid, almost odor- 
less, and boiling at 181°. Density, 1.187. It is formed by 
the action of zinc ethyl on stannodiethyl iodide. 
Sn(C-HS)'T + Zn(C-H^)' = Sn(C-H^)* + ZnP 

Staiinnudiethyl iodide. Zinc-etUyl. Stannotetrethyl. 

It is a saturated compound, and does not enter into combi- 
nation, but by the action of energetic reagents it yields com- 
pounds of stannodiethyl or stannotriethyl. Thus, with iodine, 
the following reaction takes place : 

Sn(C^IP)* + I' = Sn(C^H^)^I + C^H^I 



VOLATILE FATTY ACIDS DERIVED 
mOM THE ALCOHOLS. 



Modes of Formation and Constitution. — These acids result 
from the oxidation of the alcohols of which the principal com- 
pounds have been described. They are formed in a great num- 
ber of reactions, and many of them exist already formed in 
nature, either in the free state or in com])ination in neutral 
fatty compounds, that is, the oils and fiits. 

Their composition is expressed by the general formula C"H^" 
0"^ ; they contain one more atom of oxygen and two atoms of 
hydrogen less than their corresponding alcohols. 

Their principal modes of formation are as follows : 

1. By oxidation of an alcohol : 

CH^O + 0^ = CWO' 4- H-'O 

IMetliyl alcohol. Formic acid. 

2. By oxidation of an aldehyde: 

C^H*0 + = C^H^O^ 

Aldehyde. Acetic acid. 

3. By the decomposition of an organic cyanide with boiling 
potassium hydrate : 

CH^ CIP 

I + KOH -f H'O ^1 H- NH^ 

CN ^ ^ CO.OK ^ 

Methyl cyanide. Potassium acetate. 



VOLATILE FATTY ACIDS. 489 

The acetic acid is formed in this hist reaction, by the union 
of the carbon of the cyanoiicn group with the oxygen of botli 
the potassium liydrate and the water, the hydrogen of these 
two bodies combining with the nitrogen of the cyanogen to 
form ammonia. It may then be admitted that acetic acid con- 
tains a radical carbonyl, CO, united on tlie one hand with a 
methyl group (that of the methyl cyanide), and on the other 
with a hydroxyl group, OH. 

The other acids of the series possess an analogous constitu- 
tion. 

cip c^ii5 cnv c*H9 

CO.OH CO.OH CO.OH CO.OH etc. 

Acetic acid. Propionic acid. Butyric acid. Valeric acid. 

4. A method of synthesis, discovered by Wanklyn, furnishes 
a direct support to this theory of the constitution of the fiitty 
acids. That chemist realized the synthesis of acetic and pro- 
pionic acids by passing a current of carbonic acid gas over 
sodium-methyl and sodium-ethyl, organo-metallic compounds 
which result from the action of sodium upon zinc-methyl and 
zinc-ethyl. 

CH3 

NaCH^ + CO.O = I 

CO.ONa 
Sodium-methyl. Sodium acetate. 

02115 

NaC2H5 + CO.O = T 

CO.ONa 
Sodium-ethyl. Sodium pi'opionate. 

General Properties. — 1. The volatile fiitty acids of the series 
(^n jj2nQ2 ^^,q monobasic ; each contains one atom of hydrogen 
which may be replaced by an equivalent quantity of a metal. 

2. When submitted to dry distillation, many of their salts 
yield an acetone and a carbonate. 

CH3 



CH3-C0.0^p ., 
CH3-C0.0^^^ 


1 
= CO 

^-H3 


+ CaC03 


Calcium acetate. 


Acetone. 


Calcium carbonate. 



3. The same reaction may produce an aldehyde and a hydro- 
carbon of the series C"H"^" (Chancel). 

C3H7 
(C3HV-CO.O)2Ca = I + C3II6 + CaC03 

CHO 
Calcium butyrate. Butyral, or butyric Propylene, 

aldeliyde. 

V* 



490 ELEMENTS OP MODERN CHEMISTRY. 

4. When a mixture of a salt of a fatty acid and a formate 
is subjected to dry distillation, the principal product of the 
reaction is an aldehyde (Piria). 

CH3-C0.0K + H-CO.OK = i + K2C03 

Potassium acetate. Potassium formate. Aldehyde. 

5. The fatty acids are converted into chlorides by the action 
of phosphorus pentachloridc, or oxy chloride (Grerhardt). 

Cm^O.OK + PC15 = C-TPCCl + P0C13 + KCl 
Potassium acetate. Acetyl chloride. Phosphorus 

oxycliloride. 

C. By the action of these chlorides upon the salts of the 
fatty acids, the anhydrides of the acids are formed (Gerhardt). 

c'H'ojo + cniKoa = kci + cwojo 

Potassium acetate. Acetyl chloride. Acetic anhydride. 

7. When subjected to the action of phosphoric anhydride, 
the ammonium salts of these acids lose liU'O and are con- 
verted into nitriles or cyanogen ethers (Dumas, Malaguti and 
Le Blanc, Frankland and Kolbe). 

CH:^ CH3 

CO.O(Nn+) ^ CN 

Ammonium acetate. Acetonitrile. 

(Methyl cyanide.) 

FORMIC ACID. 

This acid, which was discovered by S. Fischer in 1760, in 
red ants, is formed in a great number of reactions, particularly 
in the oxidation of methyl alcohol, in the decomposition of 
hydrocyanic acid by acids or alkalies, in the distillation of oxalic 
acid, and in the oxidation of many organic matters, such as 
starch, sugar, etc. Berthelot achieved its direct synthesis by 
heating carbon monoxide for a long time to 100° in sealed 
flasks containing a concentrated solution of potassium hydrate. 

CO + KOH = IICO.OK 

Potassium formate. 

Preparation. — Starch, manganese dioxide, and dilute sul- 
phuric acid may be boiled together in a capacious retort, and 
the acid li(juid which condenses in the receiver saturated with 
lead carbonate. Lead formate is thus obtained, and is purified 



FORMIC ACID. 401 

by crystallization. To obtain formic acid, the salt is hcatetl in 
a cnrrent of dry hydrogen sulphide. Formic acid distils 
(Dobereiner). 

Another and better process consists in heating to 100° e([ual 
parts of oxalic acid and glycerin. Under these conditions, 
the oxalic acid breaks up into carbonic acid gas, and formic acid 
which distils. The li(juid is saturated with lead carbonate, and 
the j)reparati()n concluded as before (Berthelot). 

Properties. — Formic acid is a colorless lirpiid, having a 
pungent odor and a very acid taste. It boils at 91)°, and solid- 
ifies to a crystalline mass at 8.5°. It mixes with water in all 
proportions. 

If an excess of sulphuric acid be added to a small quantity 
of formic acid contained in a test-tube, and a gentle heat be 
applied, a regular disengagement of gas will take place ; it may 
be ignited at the mouth of the tube, and will burn with a blue 
flame. 

It is carbon monoxide, and is formed according to the fol- 
lowing equation : 

CH^O^ = CO + H^O 

If formic acid be added to a solution of silver nitrate, and 
the liquid be heated, it will soon become clouded ; silver will 
be precipitated as a gray powder, and carbon dioxide will be 
disengaged. 

The formic acid becomes oxidized in reducing the silver 
nitrate, 

CH^O' _f = CO- + H^O 

Chlorine determines an analogous decomposition. 
CH^O'^ + CP = CO' + 2HC1 

Formates. — Formic acid is an energetic acid, perfectly neu- 
tralizing the bases. It is monobasic; one of its hydrogen 
atoms can be replaced by an equivalent quantity of metal. The 
formates are soluble ; the most characteristic are ciqwic for- 
mate, Cu(CHO'^)' -\- 4H''^0, which crystallizes in magnificent, 
oblique rhombic prisms, and lead formate, Pb(CHO'j', which 
forms long, colorless needles, slightly soluble in cold water. 

Ammoniinn formate, which is obtained by saturating formic 
acid with ammonia, crystallizes in prisms which are very solu- 
ble in water. When quickly heated to about 200°, it breaks 
up into hydrocyanic acid (formonitrile) and water (Pelouze). 
(NH^jCHO' = 2H^0 4- CNH 



402 ELEMENTS OP MODERN CHEMISTRY. 



FOKMIC ALDEHYDE. 
CH20 = H-CHO 

Hofmann has recently obtained this body by the slow com- 
bustion of methyl alcohol, brought about by a spiral of jjlatinum 
wire. 

CH^O + = IPO + CH^O 

It is also formed in the distillation of barium and calcium 
formates. It is not known in the pure state. It has a great 
tendency to become polymerized, forming a solid compound, 
which Boutlerow has named trioxy methylene^ and which prob- 
ably contains C^H^O^ 



ACETIC COMBINATIONS. 

It may be admitted that these compounds contain the mon- 
atomic radical acetyl (C'HO')' = (CII^-CO)', which may be 
regarded as oxidized ethyl. 

CH3 C1I3 

-CH2 ^ ' -co 

Ethyl. Acetyl. 

Aldehyde is the hydride of this radical ; acetic acid is its 
hydrate, and acetone its methylide. Besides these, there arc 
known the oxide and chloride of acetyl, an acetyl ammonia, 
which is acetamide, etc. • 

The following formulae indicate the relations between all of 
these bodies : 

C2H30.H C2H3.0H 

Acetyl hydride (aldehyde). Acetyl hydrate (acetic acid). 

C2H30.CI (C2I130)20 

Acetyl chloride. Acetyl oxide (acetic anhydride). 

C2H30 ) 
C2H30.CH3 H \ N 

hJ 

Acetyl methylide (acetone). Acetamide. 

ACETIC ACID. 

C2IP02 

Acetic acid is the acid of vinegar. It is the product of the 
oxidation of alcohol. It is formed in a number of other reac- 
tions, among which we may mention the oxidation of aldehyde, 



ACETIC ACID. 



493 



the decomposition of metliyl cyanide by potassium hydrate, the 
action of carbon dioxide on sodium-metliyl, and the dry distil- 
hition of a great number of organic substances, such as wood, 
starch, gum, sugar, etc. 

Preparation. — The hirge quantities of acetic acid employed 
in the arts are obtained by the destructive distilhition of wood. 

The operation is conducted in large iron cylinders, heated 
directly by a fire (Fig. 123). The products of the distillation 




«mm^ 



Fig. 123. 



consist of liquids and gases. The liquids are condensed in a 
large worm, tf, cooled by a continual circulation of cold water 
through surrounding pipes mm ; the gases are conducted back 
to the fire-grate by the pipe h. The condensed product consists 
of an aqueous portion and of tar. The greater part of the 
latter is separated by a new distillation ; the first portions 
which pass contain wood-spirit, after which acetic acid distils. 
The acid liquid is neutralized by lime, and the calcium ace- 
tate formed is converted into sodium acetate by adding a solu- 
tion of sodium sulphate. The liquid, separated by filtration 
from the calcium sulphate, yields on evaporation sodium ace- 
tate, still colored brown by tarry matters. The latter are 
destroyed by fnjiug the salt, that is, by heating it for some 
time to 250^, a temperature which carbonizes the tar but does 
not afi"ect the sodium acetate. The mass is then exhausted 
with water, the solution filtered, concentrated, and crystallized. 
Crystals of pure sodium acetate are thus obtained, a salt which 
was formerly called pyroiignite of soda. Acetic acid is pre- 

42 



494 



ELEMENTS OP MODERN CHEMISTRY. 



pared by drying this salt and distilling it with 4 its weight of 
concentrated sulphuric acid. 

Or the dry salt may be decomposed by an exact quantity of 
sulphuric acid. The acetic acid which separates from the 
sodium sulphate may then be decanted, and cooled in a freez- 
ing mixture. The portion remaining li([uid is separated and 
the solid mass constitutes pure acetic acid. 

Vinegar. — A^inegar is the product of the acid fermentation 
of wine and other alcoholic liquids. The following process is 
largely employed for the conversion of wine into vinegar. It 
is the Orleans process. A small quantity of warm vinegar is 
first introduced into large vats, which have already been used 
for the operation and are impregnated with the peculiar fer- 
ment formed ; quantities of wine are then added at intervals 
of several days, the vats being maintained at a temperature 
between 24 and 27°. In a fortnight, the acetitication is com- 
plete, and a portion of the vinegar is withdrawn and replaced 
by a new quantity of wine which also becomes converted into 
vinegar. The process is thus continuous. Under these cir- 
cumstances, the alcohol is converted into acetic acid by the 
influence of a peculiar ferment that is called mother of vinegar. 

It is a vegetable product, 
a mycoderm ( Mycodcrma 
aeefi), which appears on 
the surface of the liquid, 
where it absorbs oxygen 
from the air and subse- 
quently cedes it to the 
alcohol (Pasteur). Its 
action may be compared 
to that of platinum black. 
By another process, a 
mixture of weak alcohol, 
water, and albuminoid 
matter (the juice of pota- 
toes, beets, etc.), contain- 
ing the elements neces- 
: sary for the production of 
the ferment, is allowed to 
trickle over beech-wood 
been previously steeped in 
large cask, A (Fig. 124j, 




shavings. The latter, which have 
strono' vinegar, are contained in a 



ACETATES. 495 

whore they rest upon a double bottom ])erfor:ited witli lioles. 
Tubes, tt, pass throuuli the upper portion, uiaintaiiiini»- a current 
of air which enters at the lower j)orti()n of the cask. Under 
these conditions, tlie liquid, which spreads over the shavings 
and exposes a considerable surface to the air, becomes oxidized 
with such energy that the temperature soon rises to 80° ; a 
second passage of the liquid through the casks completes the 
acetification. 

Properties of Acetic Acid. — Acetic acid is solid below 17°, 
and crystallizes in large plates. It boils at 118°. Its density 
at 0° is 1.0801. Its odor is pungent and acid. It is very 
corrosive. It mixes with water and alcohol in all proportions, 
and when it is added to Avater there is a contraction in volume. 
The maximum contraction, and consequently the maximum 
density of aqueous acetic acid, corresponds to a nuxture con- 
taining C'WO' -h H^O. 

Vapor of acetic acid passed through an incandescent porce- 
lain tube yields gases and deposits carbon, at the same time 
forming small quantities of acetone, benzol, phenol, and napli- 
thaline"(Berthelot). 

Phosphorus pentachloride converts acetic acid into acetyl 
chloride, with formation of hydrochloric acid and phosphorus 
oxychloride. 

C^H^O.OH + PCP = C^H^^O.Cl -h IICl -f POCP 

Acetic acid. Acetyl chloride. 

If a mixture of small quantities of potassium acetate and 
arsenious oxide be lieated in a test-tube, dense white vapors 
having an intense and disagreeable odor of garlic will be dis- 
engaged. 

This experiment permits the detection of minute traces of 
acetic acid ; if the latter exist in the free state in the li(|uid, 
its potassium compound must first be formed. The white 
vapor disengaged is due to a body formerly known as famiitg 
liquor of Cadet (see page 453). 

ACETATES. 

The more important neutral acetates have the composition 
R'Ceii^'OO or Il"(C-rr'02)^ according as the metal which 
replaces the basic hydrogen of the acetic acid is univalent or 
bivalent. There are many basic acetates. 

Potassium Acetate, KC'^IPO'^ — This is prepared by satu- 



496 ELEMENTS OF MODERN CHEMISTRY. 

ratinp;- acetic acid with potassium carbonate and evaporating to 
dryness. It is thus obtained in crystalUne, very deliquescent 
hunin[\3. It melts at 292°, and is very solul)le in water. 

Sodium Acetate, NaC'H'O' + 311-0. — This salt is obtained 
on a large scale in the arts in the manufacture of acetic acid. 
It was formerly called pijroUgnlte of soda. It crystallizes in 
large, obli([ue rhombic prisms, which are very soluble in water, 
and effloresce in dry air. 

Acetates of Lead.— Neutral lead acetate, Pb(CTI'0'f + 
oIl-'O, known also as sugar of lead^ is made by neutralizing 
acetic acid with litharge. It crystallizes in transparent, efflor- 
escent, oblique rhombic prisms, having a sweet and astringent 
taste. It dissolves in half its weight of cold water, and in 8 
parts of alcohol. It melts in its water of crystallization at 
75.5°. 

The neutral solution of lead acetate dissolves oxide of lead, 
forming different basic salts, according to the proportion of 
oxide dissolved. The more important of these are a dibasic 
acetate, Pb(C'H'O')' + PbO + 4H''0, and a tribasic acetate, 
PbCC'H^O-)' -{- 2PbO 4- nH-0. These two salts are gener- 
ally formed simultaneously when a solution of lead acetate is 
boiled with litharge. The solution thus obtained is used in 
medicine as Goulard's solution. If a few drops of it be added 
to ordinary river or well water, a cloud is produced, owing to 
the formation of lead sulphate and carbonate. 

If carbonic acid gas be passed into a solution of the sub- 
acetate of lead, a deposit of lead carbonate is formed. In this 
reaction, which serves for the preparation of white lead by the 
Clichy method, the excess of lead is removed from the subace- 
tate by the carbonic acid, neutral acetate being formed and 
remaining in solution. 

Acetates of Copper. — The neutral acetate Cu(C-H''0^)^ + 
ir^O, is prepared by double decomposition by mixing hot solu- 
tions of sodium acetate and cupric sulphate. The cupric acetate 
is deposited on cooling in beautiful, oblique rhombic prisms 
of a deep bluish-green color. They dissolve in 5 times their 
weight of boiling water. The dilute aqueous solution is de- 
composed by boiling, a tribasic acetate being formed, while 
acetic acid is set free. 

When cupric acetate is heated, it first loses its water of crys- 
tallization, and decomposes when the temperature reaches 240 
or 250°, disengaging acetic acid, acetone, and carbon dioxide. 



ETHYL ACETATE. 497 

The residue is linely-clivitled copper. The product of the dis- 
tiHation is a blue licjuid, which, when rectified, yields colorless 
acetic acid mixed with a small quantity of acetone. It was 
formerly called radical vinegar. 

The name verdigris is applied to a basic acetate of copper 
consisting mostly of a dibasic acetate, Cu(C-II''0")"'^ -f CuO -{- 
Gll'^O. Verdijiris is prepared by exposing to the air copper 
sheets piled up in layers with tlie pulp of grapes. In a few 
weeks the metal becomes covered with bluish crusts of verdi- 
gris, which are scraped of}' and delivered to commerce in the 
form of light-blue balls. The alcohol, formed by the fermenta- 
tion of the sugar contained in the grape-pulp, becomes oxidized 
by the air and is converted into acetic acid, and under the in- 
fluence of the latter, the copper itself absorbs oxygen. Water 
and copper basic acetate are thus formed. 

Silver Acetate, AgC'-'H'O'.— This salt, which is but slightly 
soluble in water, is precipitated when concentrated solutions 
of sodium acetate and silver nitrate are mixed. It is deposited 
from boiling water in brilliant, pearly, flexible plates, which 
darken on exposure to light. 

Ammonium Acetate, (Nll'^)C^ir^Ol — When acetic acid is 
saturated by a current of ammonia gas, this salt is obtained as 
a deliquescent, crystalline mass. It is very soluble in water 
and in alcohol. When heated, it first loses ammonia, then 
acetic acid, and acetamide finally distils. 

Ammonium acetate. Acetamide. 

It is used in medicine under the name qyirit of Mindererns. 
This is generally an impure solution of ammonium acetate, 
charged with empyreumatic matters. 

AVhen distilled with phosphoric anhydride, ammonium ace- 
tate yields methyl cyanide, or acetonitrile. 

ETHYL ACETATE. 

C2H5.C2H302 

This acetate, ordinarily known as acetic ether, is prepared 
by distilling a mixture of alcohol, sulphuric acid, and potassium 
or sodium acetate. The ethyl acetate passes over, together 
with a certain quantity of alcohol which escapes the reaction. 

42- 



498 ELEMENTS OP MODERN CHEMISTRY. 

It is purified by agitation with a solution of (.'akium eliloride, 
and the ctlier which floats is decanted, dried over calcium 
chloride, and rectified on the water-bath. 

It is a colorless li([uid having a very agreeable, ethereal odor. 
It boils at 77°. Density at 'u°, 0.9105. It is but slightly 
soluble in water, but dissolves in all proportions in alcohol and 
ether. Like all compound ethers, it is readily decomposed by 
potassium hydrate. 

C^H^C^IPO^ -f KOH = KC^ir^O^ + eiP.OH 

Ammonia converts it into acetamide and alcohol. 

C^H'O.OC-'IP + NIP = eiP.OH -f C'^H^O.Nff 

Ethyl acetate undergoes a remarkable reaction with sodium. 
The metal dissolves in the ether, forming sodium ethylate and 
the compound C"ir'NaOl 

2[C''H'0.0C'ir'] + Na^ == NaO.CTP -f C^H^NaO^ + IP 

The bodv C^IPNaO' is the sodium compound of acpAyl -acetic 
ether, CIP'^O^' = (^^H'^(C'^H''0)()-OC^IP, which is derived 
from acetic ether, C'-irH}-OC''Pr\ by the substitution of an 
acetyl group, C'H'O, for one atom of hydrogen in the radical 
acetyl. The free acetyl-acetic ether may be obtained by the 
action of hydrochloric acid upon the sodic compound CH^NaO^ 
It is a colorless liquid having an agreeable odor, and boiling at 
182°. Density at 5°, 1.03. 

SUBSTITUTION PRODUCTS OF ACETIC ACID. 

Three chlorinated acids are known which are derived from 
acetic acid by substitution : 

Monochloracetic acid C2II3C102 

Dichloracctic acid C^H-'Cl^Qa 

Trichloracetic acid C^lICl^O^ 

Monochloracetic acid is formed when a current of chlorine 
is passed into acetic acid heated to 100°, and containing a small 
quantity of iodine. As soon as chlorine begins to be disen- 
gaged at the extremity of the apparatus, the operation is arrested 
and the li((uid distilled. That portion is collected which passes 
between 185 and 187°. 

JMonochloracetic acid is solid, and crystallizes in deliquescent, 
rhomboidal tables or in prisms. It boils between 185 and 187.8°. 



ACETIC ANHYDRIDE. 499 

It is very corrosive. It is converted into glycollic acid when 
heated with an excess of potassium hydrate. 
KC-'H-'CIO^ -h KOII = KC^IIXOH)0^ + KCl 

Pofcjssiiim Potassium glycolliite. 

monoclilonicetate. 

Ammonia converts it into acetamic or amidacetic acid C'^H'^ 
(NH^COH (glycocol) (Cahours). 

?«'^^' + NII3 == HCl + ?''-''''' 
CO. OH CO.OH 

Monochlonicetic acid. Glycocol. 

Trichloracetic acid, C'^HCPO'^ a very important compound 
in the history of the science, was discovered by Dumas in IS-tO. 
It was then one of the most remarkable examples of a body 
formed by substitution, and a comparison of its properties with 
those of acetic acid led Dumas to announce the first idea of 
chemical types. 

It is obtained by exposing acetic acid to the action of a large 
excess of chlorine in direct sunlight. 

Trichloracetic acid is solid. It forms transparent and deli- 
quescent, rhombohedral crystals, fusible at 52.3°, and boiling 
between 195 and 200°. 

Its aqueous solution regenerates acetic acid by the action of 
sodium amalgam, an interesting reaction, since it furnished one 
of the first examples of inverse substitution (Melsens), as the 
replacement of chlorine by hydrogen is called. Water and 
sodium amalgam constitute a slow source of hydrogen. 

When boiled with potassium hydrate, trichloracetic acid fur- 
nishes potassium carbonate and chloroform. 

C'^HCPO' = CHCP 4- CO' 



ACETIC ANHYDRIDE. 

(C2H30)20 

This important body, discovered by Grerhardt in 1852, is 
prepared by the action of one part of phosphorus oxychloride 
on three parts of dry sodium acetate. In this operation, acetyl 
chloride is first formed, and this reacts upon an excess of so- 
dium acetate, producing sodium chloride and acetyl acetate, or 
acetic anhydride. 

C^H-O.Cl + *^'^N*it}0 = ^^'^^ + c'ffol^ 

Acetyl chloride. Sodium acetate. Acetic anhydride. 



500 ELEMENTS OP MODERN CHEMISTRY. 

Acetic anhydride is a colorless, mobile liquid, having a strong 
odor of acetic acid. It boils at 138°. When thrown into 
water, it first sinks to the bottom, and then, absorbing one mol- 
ecule of water, is converted into acetic acid, which dissolves. 

ALDEHYDE, Oil HYDRIDE OF ACETYL. 

C-'H^O 

This body was discovered by Dobereiner in 1821 ; its com- 
position and principal properties were studied' by Liebig. 

Preparation. — Aldehyde is prepared by oxidizing alcohol by 
heating it with manganese dioxide and dilute sulphuric acid, 
or better, with potassium dichromate and sulphuric acid. The 
vapors disengaged are condensed in a well-cooled receiver. The 
distilled liquid is rectified over calcium chloride, only the more 
volatile portion being collected. This is mixed with twice 
its volume of ether, and the ethereal solution saturated with 
ammonia gas. Crystals are deposited which constitute a com- 
bination of aldehyde with ammonia, and the aldehyde is ob- 
tained from them by adding a quantity of sulphuric acid exactly 
sufficient to form ammonium sulphate with the ammonia; a 
gentle heat is applied, and the aldehyde vapor is passed through 
a tube filled with calcium chloride, and finally condensed in a 
well-cooled receiver (Liebig). 

Properties. — iVldehyde is a colorless, very mobile liquid, 
having a penetrating and somewhat suffocating odor. It boils 
at 21°. It mixes in all proportions with water, alcohol, and 
ether. 

It combines with ammonia, forming aldehyde-ammonia, or 
acetylide of ammonium (Liebig). 

C^H^O.NH^ = C^H^O.NH* 

It unites with the alkaline acid-sulphites, forming crystal- 
lizable combinations. 

It is very apt to become oxidized, being transformed into 
acetic acid. 

C"^H*0 + = C^H^O^ 

If some aldehyde and a few drops of ammonia be added to 
a solution of silver nitrate, and a gentle heat be applied, the 
li(|uid soon becomes clouded, and the sides of the vessel con- 
taining it are covered with a brilliant deposit of metallic silver. 



ALDEHYDE. 501 

By the action of sodium amalgam and water, aldehyde fixes 
two atoms of hydrogen, and is converted into alcohol (A. 
Wurtz). 

C-H'O -I- H^ = C'WO 

When hydrochloric gas is passed into a mixture of aldehyde 
and absolute alcohol, monochlorethcr is formed. 

Cm^O + C2H5.0H + HCl ^ H20 + ^'^S^^ 

Monoclilorether. 

Chlorine converts aldehyde into acetyl chloride and other 
products (A. Wurtz). 

C^^H^O.H -f CP = C^ir^O.Cl + HCl 

When treated with phosphorus pentachloride, aldehj^de ex- 
changes its atom of oxygen for two atoms of chlorine, and is 
transformed into monochlorethyl chloride, C"^H*CP (ethylidene 
chloride). 

CH3 CH3 

I + PCP = I + P0C13 

CHO CHC12 

Aldehyde. Ethylidene chloride. 

Aldehyde has a great tendency to become converted into 
polymeric modifications. Among these SlTQ paraldehyde, which 
is liquid, and met aide! lyde, which is solid (Liebig). 

Dry hydrochloric acid gas converts aldehyde into ethylidene 
oxy chloride (an isomeride of dichlorether), eliminating water. 

2C'H*0 + 2HC1 = C*H«CPO + H^O 

Ethylidene oxychloride. 

By the action of hydrochloric acid diluted with twice its 
volume of water, aldehyde doubles its molecule and is converted 
into a thick, colorless, neutral body, boiling at 95° in a vacuum ; 
it is soluble in water and reduces ammoniacal silver nitrate. 
This body is uldol, C*H«0'^ (A. Wurtz). 

When heated with ordinary hydrochloric acid, aldehyde gives 
cro tonic aldehyde (Kekule). 

Aldehyde. Crotonic aldehyde. 

The same transformation takes place when aldehyde is heated 
to 100° with a small quantity of zinc chloride and a trace of 
water. 



502 ELEMENTS OP MODERN CHEMISTRY. 

ACETYL CHLORIDE. 

CH3 

C2H''0.C1 ^ V 

COCl 

This body was obtained by Gerhardt in 1852, by treating 
sodium acetate with pentaehloride, or oxychloride of phos- 
phorus. 
NaC^IPO'^ -f PCP = C^H^OCl + NaCl + POCF 

Sodium acetate. Acetyl chloride. Phosphorus oxychloride. 

It is also formed by the action of chlorine on aldehyde. 

It is a colorless, mobile liquid, having a pungent odor. It 
boils at 55°. 

If it be poured into water, it sinks to the bottom, but rapidly 
decomposes into hydrochloric and acetic acids. 

C^H'O.Cl + H'O ==: HCl + C^ffO.OH 

It undergoes a similar decomposition with alcohol, forming 
ethyl acetate and hydrochloric acid. 

C^H^^O.Cl + C^H^OH = HCl -f C^mC'ffO^ 
With ammonia, it forms acetamide and ammonium chloride. 

C^H^O.Cl + 2NH^ = NH^Cl + C^H^O.Nff 
It reacts with acetates, forming acetic anhydride. 

TRICHLORACETYL HYDRIDE, OR TRICHLORAL- 
DEHYDE. 

(chloral.) 

C2C13HO = ^^^' 
CHO 

This important body was discovered by Liebig and Dumas. 
It is formed by the prolonged action of chlorine on alcohol. 
It is a colorless, mobile liquid, having a peculiar, penetrating 
odor. It boils at 94.4° (Dumas). 

Grerhardt regarded it as aldehyde in which the three atoms 
of hydrogen of the radical are replaced by three atoms of 
chlorine. 

C^H^O.H C^CPO.H 

AMoliyde. Chloral. 

(Acetyl hydride.) (Trichloracetyl hydride.) 

Its reactions rcsomblc those of aldehyde. It forms crystal- 
lizable compounds with the disulphites. Its ammoniacal solu- 



ACETONE. 503 

tion reduces silver nitrate. These facts seem to indicate that 
chloral contains the uToup CI 10, which is characteristic of the 
aldehydes ; its constitution is then expressed by the formula 

ccr^ 

It regenerates aldehyde by the action of nascent hydrogen 
(Personne). 

The alkaline hydrates decompose it into chloroform and a 
formate (Dumas). 

eUCPO + KOH = KCHO^ + CHCF. 

Chloral. Potassium formate. 

Nitric acid converts it into trichloracetic acid, in the same 
manner that aldehyde is converted into acetic acid. 

encpo -1- = c-HCPO^ 

Chloral forms a crystallizable compound with water, C^HCPO 

CCP 
4- H'O = I ? called chloral hydrate. The latter 

^ CH(OHy -^ 

melts at 57°, and boils at 98° (Personne), being at the same 

time decomposed into anhydrous chloral and w\ater. It is very 

soluble in water. 

In contact with concentrated sulphuric acid, chloral is 
rapidly converted into a white, solid substance which is insol- 
uble in water ; it has the same composition as ordinary chloral, 
and is called insoluble chloral. 

Chloral also combines with alcohol, forming aJcolioIate of 
chloral (Personne). 

Chloral hydrate has for some time been successfully employed 
in medicine as an anodyne and hypnotic. 

ACETONE. 

C3H60 

Acetone is the methylide of acetyl, C^H^O.CH^, and since 
acetyl itself is carbonyl (carbon monoxide) methylide, CIP-CO, 
acetone can be regarded as carbonyl dimethylide, CH^-CO-CH'\ 

CO" IS co"f^S 

Carbonyl chlorirle. Carbonyl dimethylide (acetone). 

Indeed, the synthesis of acetone has been made both by treat- 



504 ELEMENTS OF MODERN CHEMISTRY. 

ing acetyl chloride with zinc methyl (Pebal and Freund), and 
by treating sodium methyl with chlorocarbonic gas (carbonyl 
chloride). 

Zn{CWy 4- 2(C^H-'^0.C1) = 2(eH'-'0.CH^) + ZnCP 

Ziuc methyl. Acetyl chloride. Acetone. 

2(CHlNa) + CO I ^} =. 2NaCl + CO | ^^3 

Sodium methyl. Carbonyl chloride. Acetone. 

Preparation. — Acetone is prepared by distilling dry calcium 
acetate in a clay retort. The vapors given off are condensed 
in a well-cooled receiver, and the liquid obtained is distilled on 
a water-bath with an excess of calcium chloride. 

Ca(C^H^O^)^ = C'R'O -f CaCO^ 

Properties. — Acetone is a colorless liquid, having a slightly 
empyreumatic, ethereal odor. It boils at 5G°. It dissolves in 
all proportions in water, alcohol, ether, and wood-spirit. 

Like aldehyde, it forms crystallizable combinations with the 
alkaline acid-sulphites. 

In presence of nascent hydrogen, produced by sodium amal- 
gam and water, it fixes H"^ and is converted into isopropyl 
alcohol (Friedel). 

CH3 CH3 



CO + 


H2 = CH.OH 


CH3 
cetone. 


CH3 
Isopropyl alcohol. 



It is seen by this method of formation that isoprop}^ alcohol 
contains a group CHOH, united to two methyl groups ; it is a 
secondary alcohol (page 473). 

Isopropyl alcohol is not the only product of the action of 
nascent hydrogen on acetone. The reaction gives rise to a 
product of condensation resulting from the addition of H"^ to 
two molecules of acetone. This has received the name pina- 
cone. 

2C^IP0 + H^ = C«H"0^ 

Pinacone. 

It is a tertiary glycol (see page 522). It constitutes a color- 
less, crystallizable mass, fusible between 35 and 38°, and boil- 
ing at 171-172°. By the action of dilute and hot sulphuric 
or hydrochloric acid, it loses one molecule of water and is con- 



ACETAMIDE. 505 

verted into a neutral liquid, boiling- at lOG^. This m pinaco- 

When acetone is added in small portions to phosphorus 
pentachloride, a very energetic reaction takes place and two 
chlorides are formed. One of them, C'lPCl' (methylchlor- 
acetol), boils at 70^. The other, C'H^Cl (monochloropropy- 
lene), boils at 23° (Friedel). 

om'o H- pcp = c^H^cp + pocp 

C^H«CP = C^H^Cl -I- HCl 

Hot, concentrated sulphuric acid removes the elements of 
water from acetone and converts it into a hydrocarbon, which 
has received the name mesifi/lcne (Kane). 

30'H«0 — 3H'0 = C^ir^ 

Acetone. Mesitylene. 

ACETAMIDE. 

C2H30.NH2 

This amide may be obtained by heating ethyl acetate to 100° 
in sealed tubes with aqueous ammonia. Alcohol and acetamide 
are formed according to the equation 

C^HIC-'H^O^ -^ NIP = C^H^^O.NH^ -f C^IP.OH 

When the resulting liquid is evaporated in a vacuum^ the 
acetamide remains. It may be purified by distillation, collecting 
that which passes above 200°. 

Acetamide is also formed by the action of ammonia on acetyl 
chloride ; one of the readiest methods of preparing it consists 
in simply distilling ammonium acetate. 

It is a solid, crystallizable body, soluble in water in all pro- 
portions. Its odor resembles that of mice. Boiling potassium 
hydrate reacts with it, forming potassium acetate and ammonia. 
Phosphoric anhydride removes from it the elements of water, 
converting it into acetonitrile or methyl cyanide. 

ACIDS OF THE SERIES C"ff"0^ 

Formic and acetic acids, of which the principal compounds 

have just been described, are the first terms of a very extensive 

homologous series. It is the series of volatile fatty acids, so 

named because it includes a great number of compounds which 

w 43 



506 



ELEMENTS OP MODERN CHEMISTRY. 



were at iBrst obtained from the natural fatty bodies, and which 
are the fatty acids proper. Amon<r the bodies congeneric with 
acetic acid, those of which the molecules are less complicated 
are liquid at ordinary temperatures ; the others are solid. The 
following table gives the nomenclature, composition, and prin- 
cipal physical properties of these acids : 

NAMES OF ACIDS. ^"^'"^ RATIOXAI, MELTING- BOILING- 

FOUMUL.E. FORMUI,.E. POINTS. POINTS, 

Formic acid .... CII202 H-CO.OH 1° 99° 

Acetic acid C2H*02 CIP-CO.OII 17° 118° 

Propionic acid . . . CUfiQ'^ C^HS-CO.OlI —21° 140.7° 

Butyric acid .... C^ll^O^ C=ni"-CO.OII 0° 163° 

Valeric acid (isovaleric) C»ll'"02 C-^IP-CO.OII 175° 

Caproic acid (isocaproic) C6II1202 CMIH-CO.OH 5° 199.7° 

(Enanthylic acid . . . C"IIi*02 C6H>:J-C0.01I 212° 

Caprvlic aci.l .... C*^ni«02 C"lli5-C0.0H 14° 236° 

Pelargonic acid . . . C911'^02 C^Hi'-CO.OII 18°(?) 260° 

Capric acid CIOH2002 C9H19-C0.0H 27.2° 

Laurie acid C12II2402 OiH2a-C0.0H 43.6° 

Myristic acid .... OnU^O'^ C'l^IpT-CQ.OH 53.8° 

Palmitic acid .... CI6II3202 C15H31-CO.OH 62° 

Margaric acid .... C^'H3*02 CieipS-CO.OH 60° 

Stearic acid CI8IP602 OUl^o-CO.OU 69.2° 

Arachnic acid .... €2011^002 C'l^HSS-CO-OH 75° 

Bcnic acid 02211**02 C2iH*3_CO.OII 96° 

Cerotic acid .... C^UV^^O'^ C26H53-CO.OII 78° 

Melissic acid .... C^ohgooz C29H5y_cO.On 88° 

We have already noticed the existence of numerous isomeric 
alcohols, and in their study the principles of isomerism have 
been explained. Such isomerides exist also in the series of 
acids, and are caused by the different atomic structure of the 
radicals, C"H^"+\ which figure in the preceding formuhie. AVe 
will consider two examples. 1. When normal butyl alcohol, 
CH-'-CH--CH^-CHlOH, is oxidized, normal butyric acid, or 
the butyric acid of fermentation, is obtained, CH'-CH'^-CH'- 
CO.OH. The acid obtained by oxidation of the butyl alcohol 
of fermentation is different from this, and the difference is 
caused by the difference in structure of the radicals (C"*!!^)'. 

Isobutyric acid, derived from the alcohol of fermentation, 

whose constitution is pTi.T^CH-CH'^.OH, contains ritj.s^ 

CH-CO.OII. 

The acid is derived from the alcohol by the substitution of 
for H'^ in the group (ClI'^OH)'. 

2. As we have already seen, the constitution of amyl alcohol 
of fermentation is expressed by the formula 



PROPIONIC ACID. 507 

^Jj3>CH-CH2-CH^OH. 

The valeric acid produced by its oxidation is then 
^H3>CH-CH^-C0.0H 

But normal valeric acid is also known, and contains 

CH '-CH^-CH^-CH^-CO.OH 
It results from the oxidation of normal amyl alcohol 

CH^-CH^-CH^-CH^-CH^OH 

Another interesting isomeride of valeric acid is trimethyl- 
acetic acid, which was discovered by Boutlerow. 

If we compare the three isomeric acids, C^H^"0^, with acetic 
acid itself, we w411 find that their isomeric relations can be ex- 
pressed in a very simple manner, by saying that normal valeric 
acid is propylacetic acid, the acid derived from the alcohol of 
fermentation is isopropylacetic acid, and lastly, that Boutlerow's 
acid is trimethylacetic acid. 



CH3 


ciPicnv) 


CH'^(CH<CH3) 


C(CH3)3 


CO.OH 


CO OH 


CO.OH 


CO.OH 


cetic acid. 


Propylacetic acid. 


Isopropylacetic acid. 


Trimethylacetic acid. 



We cannot dwell further on the subject; that which pre- 
cedes is sufficient to elucidate the isomerism of acids of the 
series C"H^"Ol 

Propionic Acid, C^H'^Ol — This acid is formed by the action 
of potassium hydrate on ethyl cyanide. It is also a product of 
fermentation ; thus, it has been obtained by allowing a solution 
of sugar, mixed with chalk and cheese, to ferment during a 
year. It is also formed in small quantity in the distillation of 
wood. 

Wanklyn made its synthesis by passing carbon dioxide over 
sodium ethyl. 

CO.b + C^H^Na = C^H^-CO.ONa 

Sodium propionate. 

Propionic acid may also be formed, though with difficulty, 
by the direct combination of carbon monoxide and ethylate of 
sodium. 

CO + C^H^ONa = C^H^-CO.ONa 



508 ELEMENTS OF MODERN CHEMISTRY. 

Properties. — It is a colorless, mobile liquid, havini^ an odor 
like that of acetic acid. It solidifies at — 21°, and boils at 
140.7°. Density at 21°, 0.996. It is miscible with water in 
all proportions. Calcium chloride separates it from its aqueous 
solution. 

There are a great number of substitution products directly 
related to propionic acid. Among these are the chlorine, bro- 
mine, and iodine derivatives, and the amides. Two of these 
derivatives are known of each particular species, presenting 
curious isomeric relations. The following examples will serve 
as illustrations : 

CH3 CH3 CH2CI CH3 CH2(XII2) 

CH2 CHCl CH2 CH(NH2) CH2 

C02H C02H C02H C021I C02H 

Propionic a-Chloropro- /3-Chloropro« a-Amidopiopi- ^-Ainidopropi- 

acid. pionic <acid. pionic acid. onic acid. oaic acid. 

Only the iodo-derivatives will be described here, and farther 
on we will mention the amides. 

a-iodopropionic ackl^ C'^H'IO', is prepared by the action of 
concentrated hydriodic acid or phosphorus iodide on lactic 
acid. 

C^H«0^ + HI = C^H^IO^ + H'^0 

Lactic acid. 

It is a thick, oily body, almost insoluble in water. 

[i-iodopropionic acid is formed by the action of concentrated 
hydriodic acid or phosphorus iodide and water on glyceric 
acid. 

CTPO* -[- SHI .= C^H^IO^ -f 2H-0 -f P 

Glyceric acid. 

It is also formed by the direct combination of hydriodic acid 
and acrylic acid, C^H^O^. 

It is a solid, occurring in crystalline laminae, fusible at 82°. 
It is very soluble in boiling water. AVhen heated to 180° 
with hydriodic acid, it is converted into propionic acid. 

C^H^IO^ -f HI = P + Q'WO' 

Normal Butyric Acid, C*H^Ol — This acid was discovered 
by Chevreul in butter, where it exists in combination with 
glycerin in butyrin. Pelouze and Gelis have shown that it 
is formed in abundance when a solution of sugar, glucose, or 
even starch is abandoned for several weeks with the addition 



BUTYRIC ACIDS. 509 

of chalk and old cheese. In about ten days a mass of calcium 
lactate is formed, but this soon disappears, gases beinii; at the 
same time disengaged. The mass again becomes li<juid, and 
the solution contains calcium butyrate. Tliis is converted into 
sodium butyrate, which is finally decomposed by sulphuric 
acid ; the butyric acid separates in the form of an oily li(|uid, 
whicii is decanted and distilled. 

Properties. — Butyric acid is a colorless licjuid, having a 
pungent and disagreeable odor which recalls that of rancid 
butter. It is quite soluble in water. Density at 14:°, 0.958. 
Boiling-point, 1G3°. 

It perfectly neutralizes the bases, forming butyrates. These 
salts, which are mostly soluble in water, have a fatty aspect. 
Calcium butyrate, Ca(C*H^O^),^ is more soluble in cold water 
than in hot water, so that its cold saturated solution becomes 
a solid mass when heated to 70°. 

Butyrone. — When calcium butyrate is subjected to dry dis- 
tillation, it yields, as principal product, butyrone, one of the 
homologues of acetone (Chancel). 

Ca(C^H^O^)^ = C^H'^0 -f CaCO'^ 

Calcium butyiate. Butyrone. 

Butyrone is a colorless liquid, lighter than water, and having 
a peculiar, ethereal odor. It boils at 144°. 

Butyral. — The principal product of the distillation of a mix- 
ture of butyrate and formate of calcium is butyral, or hutyric 
aldehyde, &W0. 

Ca(C*H^O0' + Ca(CHO^)'^ = 2CaC0^ + 2C*H«0 

This important reaction, discovered by Piria, permits of the 
conversion of butyric acid into its aldehyde ; it can also be ap- 
plied to the transformation of other acids into aldehydes. 

Butyral, which was discovered by Chancel, is a liquid, boil- 
ing at about 70°. Like aldehyde, it forms a crystallizable 
compound with ammonia, and it unites with the alkaline acid- 
sulphites as do the other aldehydes and the acetones. 

Isobutyric Acid. — An acid isomeric with butyric acid is 
known, and is designated as isobutyric acid (jMorkownikof ). 

It is formed by the oxidation of butyl alcohol of fermenta- 
tion, and exists naturally in the fruit of the Ceratonia siliqua 
(carob locust, St. John's bread). It is also obtained by decom- 
posing isopropyl cyanide with potassium hydrate. 

(C^'H^j'CN -f 2H^0 = NH^ + (C^H^'-CO'^H 
43* 



510 ELEMENTS OF 3I0DERN CHEMISTRY. 

It is a liquid having a disagreeable odor, like that of the 
acid of fermentation. Density at 20°, 0.9503. It boils at 
154°. 

Valeric Acid, C^H'^Ol — This acid was discovered by Chev- 
reul, who first obtained it from dolphin oil (phocenic acid.) It 
may be prepared by distillation of valerian root with water ; 
hence its name. It exists also in the root of angelica, in the 
Athamanta oreoselinum and in the fruit and bark of the Vibur- 
num opulus. The same acid is formed when amyl alcohol is 
oxidized by a mixture of potassium dichromate and sulphuric 
acid. 

C^H^^O + 0^ = H^O -f OWO'' 

It is also formed when potassium hydrate is boiled with iso- 
butyl cyanide, by a reaction similar to that which has already 
been indicated for the formation of isobutyric acid. 

Valeric acid is a colorless liquid, having a pungent, disagree- 
able odor. Density at 0°, 0.947. It boils at 175°. It dissolves 
in 30 parts of water, from which it is precipitated by the addi- 
tion of neutral salts. Its ammonium salt is used in medicine. 

Normal valeric acid., which has already been mentioned (page 
507), is a colorless liquid, smelling like butyric acid. It boils 
at 184-185°, and its density at 0° is 0.9577. 

Trimetliylacetic acid is formed when potassium hydrate is 
boiled with the cyanide derived from trimethylcarbinol. 

(CH^/C-CN + 2ffO = (CH')=^C-CO.OH + Nff 

It is a crystalline mass, fusible at 35°, and boiling at 163.8°. 
It dissolves in 40 parts of water at 20°. 

Caproic Acids. — There are several isomeric acids having the 
composition C^H^^O'^ One of them was discovered in butter 
by Chevreul. Normal caproic acid is formed by the oxidation 
of normal hexyl alcohol, and in the decomposition of normal 
amyl cyanide by boiling potassium hydrate. It is an oily liquid, 
having but a faint odor ; its density at 0° is 0.945, and it boils 
at 205°. Leucine., C^H^^NO'^, an important nitrogenized body 
which exists in the animal economy, is an amide, C"H^\NH^jO"^, 
of normal caproic acid. 

The caproic acid mentioned on page 50C is an isomeride of 
the preceding acid. It is obtained by decomposing, by potas- 
sium hydrate, amyl cyanide derived from the alcohol of fer- 
mentation. 



FATTY ACIDS. 511 

Our limited space will not permit of a description of all of 
the acids of this series ; we can only briefly consider the last 
menibors. 

Palmitic Acid, C^^II'-O". — This exists in palm-oil in com- 
bination with lilycerin. It is prepared on a large scale in 
England by distilling palm-oil by means of superheated steam, 
which decomposes the oil into fatty acid and glycerin. The 
fatty acids solidify on cooling. The mass is expressed to re- 
move the liquid oleic acid with which it is impregnated, and so 
obtained in dry, white cakes, which are used for the manufac- 
ture of candles. 

Margaric Acid, C^'H^^O'^. — According to Chevreul. this acid 
exists in all solid fats. To separate it from stearic acid, which 
always accompanies it, Chevreul recommends the following 
process : olive-oil is saponified with litharge and water, and the 
lead-plaster or soap thus obtained is allowed to cool; after 
separating it from the water which holds the glycerin in solu- 
tion, it is pulverized and exhausted with ether, which dissolves 
the lead oleate and leaves the margarate. The two salts being 
composed by hydrochloric acid, furnish respectively oleic and 
margaric acids. 

Margaric acid crystallizes in white scales, fusible at G0°. 
Heintz considers that the margaric acid obtained from many 
fats is a mixture of palmitic and stearic acids. 

Stearic Acid, C'^H^O"^, was obtained from tallow by Chev- 
reul. It is a solid, melting at 69.2^. After cooling, the fused 
acid becomes a laminated, white mass. It is insoluble in 
water, but dissolves in alcohol and ether. The alcoholic solu- 
tion deposits it in small pearly scales, which are not greasy to 
the touch. Stearic acid is used for the manufacture of stearin 
candles. 

The alkaline stearates are soluble in water. If a large excess 
of water be added to the solution of a neutral stearate, a crystal- 
line precipitate is formed which, according to Chevreul, is an 
acid stearate. On this reaction he has founded a method for 
the preparation of stearic acid. 

The stearates of calcium, barium, and lead are insoluble in 
water, and can be obtained by double decomposition. 

Cerotic and Melissic Acids. — These acids have been ob- 
tained from wax by Brodie (page 480). 



512 ELEMENTS OF MODERN CHEMISTRY. 



OLEIC ACID AND ITS HOMOLOGUES. 

Oleic acid, which has just been mentioned and which Chev- 
reul obtained from olein, is the principal constituent of a great 
number of oils and fats ; it does not belong to the series of 
volatile fatty acids. Its formula, C'**1I"0", shows that it differs 
from stearic acid by containing two atoms of hydrogen less 
than the latter acid. It belong^ to the series C"H'^"-'^0\ 

Pure oleic acid is an oily liquid which solidified to a crys- 
talline mass at 4°. Its alcoholic solution deposits it, when 
cooled, in small needles, fusible at l-I'^. The peroxide of nitro- 
gen converts oleic acid into a solid, crystallizable, isomeric modi- 
fication of the same acid, named by Brodie elaidic acid. 

Acrylic Acid, C^H*0^ — This is the first term of the series 
(jnjj2n-2Q2 Yi receives its name from the fact that it results 
from the oxidation of acrolein., or acrylic aldelujde., C^H*0, 
which is formed in the destructive distillation of neutral fatty 
substances and glycerin and its compounds ; it is a product of 
the dehydration of glycerin. 

Q3JJ803 ^ c'H^O -f- 211^0 

Glycerin. Acrolein. 

Acrolein reduces silver oxide, like the other aldehydes, 
being converted into acrylic acid. This acid is liquid, and boils 
above 100°. Nascent hydrogen converts it into propionic acid. 

C^'H^O^ -f W =. CWO^ 

Crotonic Aldehyde and Acid. — These two bodies are homo- 
logues of acrylic aldehyde and acid. 

C^H^O acrylic aldehyde. C3II*02 acrylic acid. 

C*H^O crotonic aldehyde. C^Il'^O^ crotonic acid. 

Crotonic aldehyde is one of the numerous transformation 
products of ordinary aldehyde. When the latter body is sub- 
jected to the action of certain salts, it loses the elements of 
water and is converted into a body which Lieben called acral- 
dchyde, but which is no other than crotonic aldehyde. 

2C2II^O = Q'WO -h H-'O 

This aldehyde is a liquid having a very irritating odor and 
an acrid taste. It boils at 103°. 

When submitted to the action of oxidizins: a^rents, such as 



POLYATOMIC COMPOUNDS — ETHYLENE. 513 

silver oxide in presence of water, it is converted into crotonic 
acid. 

Three isomeric modifications of this acid are known. One 
is Hquid, the others are solid. 



POLYATOMIC COMPOUNDS. 

After the description of the comparatively simple compounds 
which are naturally grouped with the monatomic alcohols, we 
proceed to the more complex compounds constituting the poly- 
atomic alcohols and their derivatives. The latter alcohols are 
neutral hydrates, capable of reacting with the acids to form neu- 
tral combinations analogous to the compound ethers. Those 
better known are related to the saturated hydrocarbons, from 
which they are derived by the substitution of several hydroxyl 
groups for as many atoms of hydrogen. 



C^H6 
EtJiaiie. 


C3H8 
Propane. 


Cniio 
liiitane. 


C6HU 
Ilexane. 


C2I1*(0H)-'' 
Etlijiene dihydrate 

1 glycol). 


Glyceryl tri- 
hydrate (glycerin). 


C*H6(0H)* 
Erythiite. 


C6II8(01I)6 
Mannite. 



By oxidation of these polyatomic alcohols, polyatomic acids 
are produced which bear the same relation to the former that 
acetic acid bears to ordinary alcohol. 

It will be noticed that the radicals of these alcohols are un- 
saturated hydrocarbons, that is, they contain less hydrogen than 
the saturated hydrocarbons, C"H^"^^ Of these radicals, only 
those can exist in a free state which contain an even number 
of atoms of hydrogen. We will briefly consider the more 
important of them. 

ETHYLENE. 

C2H* = CH2=:CH2 

This gas, formerly known as olefiant gas or heavy carbu- 
retted hydrogen, is formed in a great number of reactions. It 
is produced, together with other hydrocarbons, when substances 
rich in carbon and hydrogen, such as fats and resins, are de- 
composed by dry distillation, that is, by the destructive action 
of heat. 



514 ELEMENTS OF MODERN CHEMISTRY. 

Preparation. — It is obtained in the laboratory by dehydrat- 
ing alcohol by a large excess of sulphuric acid. Ordinarily, a 
mixture of one part of alcohol and 4 parts of concentrated sul- 
phuric acid is heated in a flask containing almost enough sand 
to absorb the entire liquid. The gas disengaged is passed 
through a wash-bottle containing potassium hydrate, and may 
then be collected over water. 

Towards the close of the operation the liquid blackens, and 
much sulphurous and carbonic acid gases are disengaged. 
These are absorbed by the potassa in the wash-bottle. 

The following equation expresses the reaction by which 
ethylene is formed : 

c^H«o = cm' + H^O 

Composition and Properties. — Ethylene is a colorless gas, 
having a feeble, ethereal odor. Its density is 0.9784 compared 
to air, or 14 compared to hydrogen. 

Its composition may be deduced from the following experi- 
ment : 

2 volumes of ethylene (2 cubic centimetres, for example) 
and 6 volumes of oxygen are introduced into an eudiometer 
over mercury. After the passage of the spark, the 8 volumes 
will be found to be reduced to 4 volumes, all of which will be 
entirely absorbed if a solution of potassium hydrate be passed 
into the tube. The 4 volumes are therefore carbon dioxide. 

4 volumes of carbon dioxide represent 2C02. 

2 volumes of ethylene therefore contain C'^. 

4 volumes of carbon dioxide contain but 4 of the 6 volumes of oxygen 
employed ; the other two have therefore been used in the formation of 
water and have burned 4 volumes of hydrogen. 

2 volumes of ethylene then contain 4 volumes of hydrogen. 

Eudiometric analysis therefore indicates the composition of 
ethylene to be 

C'H* = 2 volumes. 

This gas is inflammable and burns in the air with a brill- 
iant flame. When mixed with three volumes of oxygen and 
ignited, it produces a violent explosion. 

It is slowly absorbed by concentrated sulphuric acid, ethyl- 
sulphuric acid being formed. AVhen ethylene is heated with 
hydriodic acid, the two bodies combine directly to form ethyl 
iodide. 

If one volume of ethylene and two volumes of chlorine be 



ETHYLENE. 515 

rapidly mixed in a tall jar, and a liulitcd match be applied, the 
mixture takes tire and burns with a red flame extendin;j; to the 
bottom of the jiir, which becomes covered with a black deposit 
of carbon. 

C-H* -f- 2CP = 4IIC1 + e 

If equal volumes of ethylene and chlorine be mixed and ex- 
posed to diffused light on the pneumatic trough, the water will 
soon rise in the jar, and the two gases will disappear. At the 
same time, oily drops will appear on the sides of the jar and 
upon the surface of the liquid. The body so formed is a li(j[uid 
insoluble in water, and results from the direct combination of 
ethylene and chlorine. It was form'erly called Dutch liquid, 
or Dutch oil (hence the old name olefiant gas) ; it is now called 
ethylene chloride. Its composition is expressed by the formula 
C-HTT. It boils at 82.5°. 

If a small quantity of bromine be poured into a large flask 
filled with ethylene, and manipulated so that the bromine may 
form a thin layer on the sides of the flask, an elevation of tem- 
perature will be observed, and the liquid will rapidly become 
colorless. The bromine has combined with the ethylene to 
form a colorless liquid, ethylene bromide^ boiling at 131°. 

Ethylene iodide, C^H^P, may be obtained by introducing 
iodine into large jars filled with ethylene, and exposing to dif- 
fused light during several days. The iodine is little by little 
converted into a solid, white body, which may be purified by 
crystallization in alcohol ; it is ethylene iodide. 

Chloro-Derivatives of Ethylene and Ethylene Chloride. — 
If ethylene chloride be heated with an alcoholic solution of 
potassium hydrate, a brisk reaction soon takes place. A gas 
is disengaged and may be collected over water ; on contact 
with a lighted taper, it burns with a flame tinged with graen. 
This gas is chlor ethylene. It is formed according to the fol- 
lowing equation : 

C^H^CF + KOH = WO + KCl + C'H^Cl 

Like ethylene itself, chlorethylene will combine directly with 
two atoms of chlorine, forming chlorethylene chloride, C'"H''C1. 
Cl'^, which may also be obtained by the action of chlorine on 
ethylene chloride. 

Chlorethylene chloride is decomposed by alcoholic potassa, 
like ethylene chloride. ^Yater, potassium chloride, and dichlor- 
ethylene are formed. 



516 ELEMENTS OP MODERN CHEMISTRY. 

C^H^CP -h KOH = WO + KCl + CmV\' 

Chlorethylene cliloriae. Dichlorelhylcnp. 

In its turn, dichlorethylene can fix two atoms of chlorine, 
forming dichloretliylcne chloride. 

These reactions have permitted the preparation of two 
classes of chloro-compounds, — one derived from ethylene chlo- 
ride, the other from ethylene itself. 

C2H*C13 ethylene chloride. 
C2H3C13 chlorethylene chloride. 
C2IPC14 dichlorethylene chloride. 
C^HCl^ trichlorethylene chloride. 
C'^Cl^ carbon sesquichloride. 



C'-^II* ethylene. 
C2II3C1 chlorethylene. 
C2H2C12 dichlorethylene. 
C2HC13 trichloretliylene. 
C2Cl'i tetrachlorethylenc. 



DENSITIES. 


BOILING-POINTS. 


1.256 at 12P 


82.5° 


1.422 at 17° 


115° 


1.576 at 19° 


137° 




158° 




182° 




—18 to— 15° 


1.250 at 14° 


35 to 40° 




87 to 88° 


2.619 at 20° 


116.7° 



Regnault, who carefully studied these bodies, has shown 
that the terms of the first series are isomeric with the chloro- 
derivatives of ethyl chloride, wdth the exception of the last 
tw^o, which are the same in both series. 

That we may more thoroughly understand this isomerism, 
we will consider ethylene chloride, C'H^CP, and its isomeride 
dichlorethane, called also ethylidcne chloride. In the first, 
two atoms of chlorine are united, each to a diff'erent atom of 
carbon ; in the second, both are united to the same carbon 
atom. 

CH2C1 CIIC12 

CH-'Cl CII3 

Ethylene chloride. Ethylidene chloride. 

Tetrachlorethylene was discovered by Faraday in 1821. It 
is formed by the action of alcoholic potassium hydrate on tri- 
chlorethylene chloride. 

C^HCP = e'CP + HCl 

It is also formed by the action of a red heat on carbon 
sesquichloride. 

C'^CP = C^CP + CP 

It is a very mobile liquid, which does not solidify at — 18°. 
It absorbs chlorine under the influence of direct sunlight, being 
transformed into carbon sesquichloride, C-^CP. 



HOMOLOGOUS SERIES, C"!!"". 517 



HOMOLOGOUS SERIES, C"IP" 

Ethylene is tlie first member of a rich series of homologues, 
of which we will summarily describe a few of the others. It 
is, however, important to remark that since ethylene is (CH-')'', 
it would seem that the constitution of the superior hydrocar- 
bons of the series should be expressed by the formula (CH^)". 
Thus far none of these normal hydrocarbons have been isolated. 
For example, normal propylene, CH'^-CH^-CH'', is unknown. 
The compound C^H*', which will shortly be described, is an 
isomeride of normal propylene, and its constitution is expressed 
by the formula CH -CH=CH^ It absorbs chlorine directly, 
forming the chloride 

Cff-CHCl-CH^Cl 

Above the fourth member of this series, butylene, the 
number of isomerides increases rapidly. Thus, the butylene 
derived by dehydration from butyl alcohol of fermentation is 

cS3>C=CIP 

It is formed according!; to the following: reaction : 

^{]3>CII-CH2.0H — IPO = ^J|3>C=CIP 

Independently of this butylene, there are two others, the 
formation and principal properties of which will be indicated 
farther on. 

Their constitutions are expressed by the formulae 
CH3-CH=CH-CH3 
CH3-CH2-CH=CH2 

The isomeric relations of these three butylenes may be repre- 
sented in a very simple manner if we consider them to be 
derived from ethylene, H"^C=CH'^, the hydrogen of which is 
partly replaced by methyl or ethyl. The following compounds 
are thus obtained : 

Dimethylethylene a (CH3)2C=CH2, boils at —6°. 

Diraethvlethylene p (normal) (CH3)HC=CH(CH»). boils at +3°. 
Ethylethylene (C2H5jHC=CH2, boils at —5°. 

The fifth member of the series, amylene or jjenfene, C^H'", 
presents still more numerous isomerides, but they can all be 
explained by the principles already exposed : they may be re- 

44 



518 ELEMENTS OF MODERN CHEMISTRY. 

garded as derivatives of etliylene by the substitution of a pro- 
pylic or isopropylic group for one atom of hydrogen, or by the 
substitution of an ethyl group and a methyl group for two 
atoms of hydrogen, or lastly, by the substitution of three methyl 
groups for three atoms of hydrogen. 

Propylene, C'PP. — To prepare this gas in a pure state Ber- 
thelot and de Luca heat allyl iodide with mercury and concen- 
trated hydrochloric acid. 

2CTPI -f- 4Hg + 2HC1 = Hg-'CP + Hg-P + 2CTP 

Propylene is a colorless gas, having a feeble, alliaceous odor. 
It is rapidly absorbed by sulphuric acid, with formation of 
isopropylsulphuric acid (Bert helot). 

03116 + H2S0* = ^^^^^yj>SO* 

It unites directly with hydriodic acid, forming an iodide 
which is isomeric with propyl iodide. 

cm' -f HI = (CII')'I 

Propylene unites directly with chlorine and bromine, forming 
propylene chloride, C^IPCP, and propylene bromide, C^H^Br. 
The latter is a colorless liquid, boiling at 145°. 

The propylene just described is not normal propylene, (CH'^)^. 
Its constitution and that of its bromide are expressed by the 
formultTe 

CH^-CH=CH2 CH^-CHBr-CH-Br 

Propylene. Propylene lironiitle. 

Normal propylene is not known, but the corresponding bro- 
mide exists. It has been obtained by heating allyl bromide, 
C^H^Br, with hydrobromic acid. 

CH2=CH-CffBr + HBr = CH^Br-CH--CH-Br 

Allyl bromide. Normal propyU-ne bromide. 

The latter bromide is a colorless liquid, boiling at 1G5°. 

BUTYLENES, C*H«. 

1. Dimethylethylene «, (CII^)T=CIP. — This body is 
formed when isobutyl alcohol is dehydrated by zinc chloride, 
or by the action of alcoholic potassium hydrate on ])utyl iodide, 
C^H^I. It boils at — G°. It unites directly with hydriodic acid, 
forming tertiary butyl iodide, (CH^)"''CI-CH^. and combines 



AMYLENES. 511) 

with bromine, formint!; the bromide (CH')'^CBr-CH'^Br, which 
boils at 141)°. 

2. Dimethylethylene /5, (normal or symetric) (CH'^)HC= 
Cll(Cli'). — Is t'ormod by the action of ak-oholie potassa on 
secondary butyl iodide, Cir'-CH'-CHI-Cir'. Boils at +8° 
and solidifies to a crystalline mass at 0°, Unites with III, 
rcLrcneratiiiii; secondary butyl iodide, and with bromine, i'orming 
the bromide (CIP)HBrC-C]IBr(Cir), which boils at 151)°.' 

De Luynes obtained secondary butyl iodide by reducing 
erythrite with a lariie excess of hydriodic acid (page 505). 

3. Ethylethylene (ethyl-vinyl), (C^lP)IiC-CH^—Ts ob- 
tained by the action of sodium on a mixture of ethyl iodide 
and bromethylene. 

C21I5I + BrH 0=0112 + Na2 = NaT + NaBr + (C2II5)IIC=CH2 
Boiling-point, — 5°. It unites with HI, forming secondary 

butyl iodide, and with bromine, forming the bromide CIP- 

CH^-CHBr-CH^Br, boilin- at 1GG°. 



AMYLENES, OR PENTENES, C'R'', 

Several isomeric hydrocarbons are known of the composition 
^sjjio Xhey exist in unequal proportions in the product of 
the reaction of zinc chloride on amyl alcohol, a product gener- 
ally designated as amylene. It is prepared by heating amyl 
alcohol with zinc chloride, and passing the vapors which are 
giyen off into a well-cooled receiver. The product is rectified, 
that portion being retained wliich passes below 40°. It is a 
mixture of isomeric amylenes, whose boiling-points vary from 
22 to 40°, and which result from the dehydration of aniyl 
alcohol. 

We need only describe two of these isomeric hydrocarbons: 
trimethylethylene, which constitutes the greater portion of the 
mixture, and isopropylethylene. 

Trimethyhthi/lene or ordhiary amylene may be obtained in 
a pure state by dehydrating tertiary amyl alcohol (the hydrate; 
of amylene of Wurtz), which may be accomplished by simply 
heating it. 

(CIP)2=zC(OII)-CH2-OH3 — H20 = (CI13)2C=CII(CH3) 
Tertiary amyl alcohol. Triniethylctliylene. 

It boils at 3G°, and unites directly with hydriodic acid, form- 
ing tertiary amyl iodide, (CH^^j'CI-CH'-CIP, which boils at 
129° 



520 ELEMENTS OP MODERN CHEMISTRY. 

When bromine is poured into cooled amylene, the addition 
of each drop produces a hissini:; noise, indicatinu' a violent reac- 
tion, and the product is a licpiid amylene bromide, boiling be- 
tween 170 and 180°. If the operation be performed upon crude 
amylene, a mixture of several bromides will result. Trimethyl- 
ethylene yields a bromide containing (CtF)"=CBr-CHBr-ClP. 

Isopropylethylene is formed by the action of alcoholic potas- 
sium hydrate on amyl iodide (Flavitzky). 

^Jp>CH-Cn2-CIl''I — HI := ^,}{3>CII-C1I=CH2 
Amyl iodide. Isopropylethjlene. 

This body also exists in small quantity in the mixture of 
hydrocarbons formed by the action of zinc chloride on amyl 
alcohol. Boiling-point, 25°. It unites with hydriodic acid, 
forming a secondary iodide, (CH"^)"-=CII-CHI-CH\ which boils 
at 137-139°. It combines with bromine, forming the bromide 
(CH^)'^=CH-CHBr-CH^Br, which boils between 180 and 190°. 

Polymerides of Amylene. — By the action of zinc chloride 
on amyl alcohol, there are formed, independently of amylene, 
other hydrocarbons, among which are the polymeric modifica- 
tions known as diamylene, C^^H"" ; triamylene, C^^H^" ; tetra- 
mylene, C^"H" (Balard, Bauer). These bodies are formed by 
the union of one, two, three, or four molecules of amylene. 

HYDROCABBONS OF THE SERIES C"H-»-l 

Among the more simple hydrocarbons is one which was dis- 
covered by E. Davy, and which Berthelot has recently suc- 
ceeded in preparing by various processes. It is acetylene, and 
is the first member of a series which includes, among others, 
the following hydrocarbons : 

Acetylene C2H2 (E. Daw, Berthelot). 
Allylene C^H-t (Sawitsch). 
Crotony!ene ('■*11'' (E. Cnventou). 
Valeiylene C^H^ (Reboul). 

Acetylene, C-H^ = CH~CH. — This gas is produced by the 
incomplete combustion of many organic substances rich in car- 
bon (Berthelot). 

If a few drops of ether be poured upon the surface of an 
ammoniacal solution of cuprous chloride contained in a nar- 
row jar, and its A^apor be ignited, a brownish-red deposit of 
acetylenide of copper will be formed and may be observed on 



DIATOMIC ALCOHOLS. 521 

flowing the liquid around on the sides of the jar. This reac- 
tion is characteristic of acetylene. 

Tliis gas may be formed by tlie direct union of carbon and 
hydroiicn, as discovered by Berthelot, when the electric arc is 
passed between carbon points in a vessel containing pure hydro- 
gen. At the high temperature of the arc, the hydrogen com- 
bines directly with the carbon, forming acetylene. 

It is also formed when monobromethylene is heated with 
amylate of sodium (the sodium compound of aniyl alcohol) 
(Sawitsch). 

en^Br 4- C^H^.ONa = C^FP + O'H^VOH -f- NaBr 

Monobroni- Amylate of sodium. Acetylene. Amyl alcohol, 

ethylene. 

Acetylene is a colorless gas, having a peculiar and disagree- 
able odor. It is quite soluble in water. It burns with a bright 
but smoky flame. It forms two compounds with bromine, a 
dibromide, C-H-^Br^, and a tetrabromide, C'H'Br\ 



DIATOMIC ALCOHOLS, OR GLYCOLS. 

The name glycols was given by Wurtz to the dihydrates of 
the series of hydrocarbons, C"H"^". If ordinary alcohol be 
ethyl hydrate, ordinary glycol is ethylene dihydrate. 

C^H^OH cmxoRf 

Ethyl hydrate. Ethylene dihydrate. 

While alcohol reacts with a single molecule of a monobasic 
acid to form a neutral ether, glycol can react with either one 
or two molecules of a monobasic acid, thus forming two ethers. 
In other words, while the monatomic alcohols contain but one 
atom of hydrogen which is replaceable by a single radical of a 
monobasic acid, glycol contains in the two groups OH two such 
atoms of hydrogen, capable of being replaced by 2 radicals of 
a monobasic acid, or one radical of a dibasic acid. 

C2H30 1 " (cnpoy^ \ ^ (c*n*02j" [ ^ 

Ethyl acetate. Ethylene diacetate. Ethylene succinate. 

The glycols yield diatomic acids by oxidation. 
There are isomeric glycols, or isoglycoh^ corresponding to 
the isoalcohols which have already been defined (page 473). 

44* 



522 ELEMENTS OP MODERN CHEMISTRY. 

Six glycols are now known, belonging to the series C"H^"+^Ol 



Ethylene glycol, or glycol . . 
Propylene glycol, or propylglycol 
Butylene glycol, or butylglycol 
Amylene glycol, or amylglycol . 
Hexylene glycol, or hexylglycol 
Octylene glycol, or octylglycol (Ph 
de Clermont) 





DKNSITY AT 0^. DOILING-J'OINTS 


0211602 


1.126 197.5° 


C3II802 


1.051 188-189° 


CiW0()2 


1.048 183-184° 


C5 111202 


0.987 177° 


Ceiiuo-! 


0.9667 207° 



C8H1602 

It is to be remarked tliat all of the members of the above 
series are not, strictly speaking, homologous. 

The structure of the latter glycols is different from that 
of ethylene glycol ; they are isoglycols. The prop^'lglycol 
discovered by Wurtz is of this number. Normal propylglycol 
has recently been discovered by Greromont, and obtained in a 
pure state by Reboul. 

The isomerism of the glycols, like that of the alcohols, is 
due to the constitutions of their molecules, which can contain, 
like the molecules of the alcohols, the following groups : 

The primary group -CIP.OII 
The secondary group =CH.OH 
The tertiary group ^C.OH 

Thus, ethylene glycol is primary, since it contains two groups, 
CH^OH. 

The amylglycol derived from trimethylethylene is at the 
same time secondary and tertiary. 

Pinacone, which has already been mentioned (page 504), is 
a tertiary glycol ; it contains two groups ^(C.OH). 

CH2.0H CH^^ ^-^^ CH3> 9-^^ 

CII2.0H CH-^-CH.OH CH3^ ^''^^ 

Glycol. Amylslycol. Pinacone. 

(Secondary and tertiary.) (Tertiary.) 

Among the mixed glycols, that is, those containing at the 
same time two different alcoholic groups, is ordinary propyl- 
glycol, which is primary and secondary. 



CIROH 


CH3 


CH2 


CH.OH 


CH2.0H 

NorniHl propvlglycol. 
(Primary). 


CH2.0H 

Ordinary propylglycol. 
(Primary and secondary) 



GLYCOL. 523 

GLYCOL, OR ETHYLENE DIHYDRATE. 

C2H602 = C^H*(OH)-^ 

AYurtz first obtained glycol by causing either iodide or bro- 
mide of ethylene to react with silver acetate 

C^il^l^ + j^°Q2ii:i02 — ^^ ^^ ) {C2H302 + "^^g^ 
Silver acetate. Ethylene diacetate. 

and saponifying the resulting ethylene diacetate by potassium 
hydrate. 

g|{3^;^|(C2H*)"+ 2K0H = 2(Cm30.0K) + (C^IP)" | ^J{ 
Ethylene diacetate. Potassium acettite. Glycol. 

Atkinson has shown that the silver acetate may be advan- 
tageously replaced by an alcoholic solution of potassium ace- 
tate. Bromide of ethylene reacts with the latter salt, forming 
potassium bromide, which is almost insoluble in alcohol, and 
ethylene acetate which is afterwards decomposed by caustic 
potassa or caustic baryta. 

Another process has been recently proposed by Hiifner and 
Zoller. 188 grammes of ethylene bromide, 138 grammes of 
potassium carbonate and 1 litre of water are introduced into a 
large flask connected with a reversed condenser, and the mix- 
ture is boiled until all of the ethylene bromide has disappeared. 
The aqueous liquid is then concentrated on a water-bath, and 
alcohol is added to precipitate the potassium bromide ; the 
alcoholic liquid is then distilled. Alcohol and water first pass, 
and when the temperature rises above 150°, the liquid which 
condenses is nearly pure glycol. 

Properties. — Grlycol is a somewhat syrupy, colorless, and 
odorless liquid, having a sweet taste. It mixes with water and 
alcohol in all proportions, but is scarcely soluble in ether. It 
boils at 197.5°, and distils without alteration. 

Its analogy to alcohol, from which it difi"ers by containing 
one more atom of oxygen, is demonstrated by the following 
experiments : 

1. If platinum black be moistened with glycol and then 
rapidly plunged into a jar of oxygen, a brilliant incandes- 
cence is manifested immediately, due to the energetic absorp- 
tion of oxygen. 



524 ELEMENTS OF MODERN CHEMISTRY. 

With dilute glycol, the oxidation is slower, and glycollic acid 
is formed. 

CH2.0H CH2.0II 

I 4-02 I 4- TJ20 

CIRC II + ^ — CO.OH ^ -^ ^ 
Glycol. Glycollic acid. 

2. If glycol be heated with ordinary nitric acid, torrents of 
red vapor are disengaged, and the liquid deposits crystals of 
oxalic acid on cooling. 

CH2.0H CO.OH 

tiROH +202= .^^jj +2H20 
Glycol. Oxalic acid. 

3. When glycol is heated with potassium hydrate to 250°, 
pure hydrogen is disengaged and potassium oxalate is formed. 

Q2U6Q2 j^ 9I^0H = C2Q.J^2 _^ ^^2 

Glycol. PoUissium oxalate. 

These experiments establish between glycol and glycollic and 
oxalic acids, relations analogous to those which exist between 
alcohol and acetic acid. 

Ethylene Chlorhydrate, or Ethylenic Chlorhydrin. — 
When hydrochloric acid gas is passed into glycol, a neutral 
compound is formed which constitutes the monocldorhydrin 
of glycol^ or etlnjlene chlorhydrate. 

C2H*<J^JJ + HCl = C2II^<^f^ + H20 
Glycol. Ethylene chlorhydrate. 

This compound is intermediate between glycol and ethj'lene 
chloride, which is the dichlorhydrin of glycol. 



C«H.<OH 


C2H*<2jH 


C2II4<g 


Glycol. 


Monochlorhvdrin of 


Dichlorhydrin of {rlvcol 




glycol. 


(ethylene chloride). 



Ethylene chlorhydrate is also formed by the direct union of 
ethylene gas and hypochlorous acid (Carius). 

Q'W + HCIO = Q'WQIO 

It is a colorless liquid, having a density of 1.24 at 8°. It 
boils at 130-131°. 

Ethylene hromhydrate, or ethylenic hromhydri\ is formed 
under circumstances analogous to those which furnish the 
chlorhydrate. It is a thick, colorless liquid, boiling at 147°. 



ETHYLENE OXIDE. 525 

Ethylene Nitrates. — By tlie reaction of ethylene brom- 
hydrate on silver nitrate, at ordinary temperatures or by the 

aid of gentle heat, ethylene mononitrate, C'-ir'<^AJ"r , is 

obtained as a colorless or slightly yellow liquid, which is sol- 
uble in water. Density at 11°, 1.31. 

NO^ 

Ethylene dinitrate, C^H*<^Q\yQ2j is formed by the action 

of ethylene bromide on an alcoholic solution of silver nitrate. 
It is a mobile, colorless liquid, insoluble in water. Density at 
8°, 1.4837. It explodes by percussion (Henry). 

Ethylene Acetates. — When glycol is heated with acetic 
acid, it is converted into acetic ethers. 

C2H*<Q^ + C2H30.0H = C2H4<^^'^^^ + H20 

Acetic acid. Ethylene nionacetate. 

C2H*<^^ + 2(C2H30.0H) -= C2H4<Q-™3^ + 2H20 
Acetic acid. Ethylene diacetate. 

Ethylene monacetate, or monacetic glycol, is a liquid mis- 
cible with water and alcohol, and boiling at 182°. 

Ethylene diacetate, or diacetic glycol, can be prepared by the 
reaction of ethylene iodide on silver acetate. It is a colorless 
liquid, soluble in 7 parts of water; it boils at 186°. 

It is thus seen that two neutral ethereal compounds can be 
formed by the action of one and the same monobasic acid on 
glycol, while the monatomic alcohols would furnish but a single 
compound ether under the same circumstances. 

ETHYLENE OXIDE. 
CH2 

If an excess of potassium hydrate be added to ethylene 
chlorhydvate contained in a test-tube, and a gentle heat be 
applied, a brisk effervescence will take place, due to a dis- 
engagement of vapor which may be ignited at the mouth of 
the tube. 

At a low temperature, this vapor condenses to a colorless 
liquid, which is ethylene oxide. 

C^H^CIO = C^H^O + HCl 

Ethylene chlorhydrate. Ethylene oxide. 



526 ELEMENTS OF MODERN CHEMISTRY. 

Ethylene oxide has the composition of glycol, less the ele- 
ments of one molecule of water. 

C^H*0 = C'H«0^ — H'O 

However, it cannot be obtained by direct dehydration of 
glycol, for when that body is distilled with zinc chloride, 
among other products, aldehyde, which is isomeric with ethyl- 
ene oxide, is obtained. 

Greene has obtained ethylene oxide by double decomposi- 
tion, by heating ethylene bromide with anhydrous sodium 
oxide. 

C^IPBr^ + Na^O = C'H*0 + 2NaBr 

Properties. — Ethylene oxide boils at 13.5^. It dissolves 
in all proportions in water, alcohol, and ether. Under the 
influence of sodium amalgam and water, it fixes hydrogen 
directly, being transformed into alcohol. 

C^H^O + H^ = C^H^O 

It combines directly with water at 100°, regenerating glycol. 

It possesses basic properties. 

If equal volumes of hydrochloric gas and vapor of ethylene 
oxide be mixed over the mercury-trough (the mercury should 
be slightly warmed ) the two gases will disappear ; they combine 
to form a liquid which is ethylene chlorhyclrate. 
eH*0 + HCl = C-IPCIO 

If liquid ethylene oxide be added to a cooled solution of 
magnesium chloride, an abundant precipitate of magnesium 
hydrate will be formed in the course of a day, and the liquid 
will contain ethylene chlorhydrate. Oxide of ethylene precipi- 
tates magnesia as would a powerful base (A. Wurtz). 

If a fragment of zinc chloride be allowed to fall into ethylene 
oxide, the latter soon undergoes a curious, polymeric change, 
and becomes solid (A. Wurtz). 

Bases Derived from Ethylene Oxide. — Oxide of ethylene 
combines with ammonia, yielding a series of bases, the hijdrox- 
ethylenamiiies^ which are formed by the direct union of one, 
two, or three molecules of ethylene oxide with one molecule of 
ammonia. 



c^iRoin 


C'IROII ) 


C^IIt.OII \ X 


11 In 


C2IR01I \ N 


HJ 


II ) 


C'^H^.OII ) 


Hydroxethylenamine. 


Dihydioxethylenamine. 


Trihydroxethylenamine. 



ETHYLENE-DIAMINES. 527 

These bases are also formed by the action of ammonia on 
ethylene chlorhydrate. 



CI 



C211^.0II 



C2H*<^' + NJI3 =. II ^ N + IICl 



■OH 



II ^N 



nl 



When ethylene chlorhydrate is treated with trimethylamine, 
the bodies combine, forming a chloride. 

N(cn3)3 + c-^i,.<oii = c™}n.ci 

AVhen this chloride is treated with water and silver oxide, 
it is converted into a hydrate. 

C^H^.OH ) 

This hydrate is iieurine, an energetic natural base which 
exists in the bile (choline) and which is also a product of the 
decomposition of a complex substance, lecifhtne, which exists 
in the brain, in the nerves, and in the yolk of eggs. 



ETHYLENE-DIAMINES. 

These bases result from the substitution of one, two, or three 
ethylene groups, (C'-H^)", each for two atoms of hydrogen in 
two molecules of ammonia. 

They are formed by the reaction of an alcoholic solution of 
ammonia on ethylene bromide at ordinary temperatures. 

C2H4Br2 + 2NH3 = C2H*(NH2)2.2HBr 
Ethylene-diamine 
hydrobromide. 

CH2-NH2 r(C2H*)" 

Ethylene-diamine, ^j^.j^^z ^^^ ) "^ ^^ ^ liquid base, 

boiling at 123°. By the prolonged action of an excess of 
ethylene bromide, it is converted successively into diethylene- 
diamine and triethylene-diamine. 



{{Q.ni^)" f(C2m)" r(C2n*)" 

N2Jh2 WliCm^)" N2^(C2II4)" 

[W [W ((C2H*)" 

Ethylene-diamine. Diethylene-diamine. Triethylene-diamine. 



Diethylene-diamine boils at 170°, and triethylene-diamine at 
210°. They are liquids. The ethlylene-diamines are diacid, 
that is, they combine with two molecules of a monatomic acid, 
such as hydrochloric or hydrobromic acid (Hofmann). 



528 ELEMENTS OF MODERN CHEMISTRY. 



ISETHIONIC ACID. 

C2H6SO^ = C-^H^<g«Qj^ 

This acid, which has long been known, attaches to the eth}^- 
lene derivatives. Oxide of ethylene unites directly with sodium 
acid-sulphite (bisulphite), forming sodium isethionate. 

C^HiO + ^^>S03 = G'ii'<^os^^ 

Sodium isetliionate. 

The same salt is formed when ethylene chlorhydrate is heated 
with neutral sodium sulphite. 

C2n*<^f^ + Na2S03 = C'H*<gJj5j^^^ + NaCl 

Isethionic acid may also be obtained by passing the vapor of 
sulphuric anhydride into cold absolute alcohol or ether ; the 
liquid is then mixed with four times its volume of water, and 
boiled for several hours, after which it is neutralized with 
barium carbonate. The filtered liquid contains barium isethi- 
onate, which, when exactly decomposed by sulphuric acid, fur- 
nishes isethionic acid. 

Isethionic acid is a sour liquid which cannot be entirely 
deprived of water without decomposition. Its salts are very 
stable. It is isomeric with ethylsulphuric acid. Phosphorus 
pentachloride transforms it into a chloride. 

C2H4<^J^ Qj. + 2PC15 ^ C2H4<;^J^2.ci + "CI + KCl + 2POC13 

Potassium isethionate. Chloreth.vlsulphuroiis 

chloride. 

The latter body is a liquid, boiling at 120° ; it is decomposed 
by the action of water at 100°, into chlorctliijlsul^ihuroiis acid 
and hydrochloric acid. 

^'«*<S02.C1 + ^^"^ = C'"'<S02.0IT + "^^ 
Chlorethylsulphurous acid. 



TAURINE. 

C2H7NSO^ 

This important acid, whose existence in the bile was dis- 
covered by Gmelin in 1 824, is related to isethionic acid ; it is 
omido- isethionic acid, that is, it is derived from the latter acid 



PROrYLGLYCOLS — GLYCERIN. 529 

by the substitution of a group Nff for a group Oil. It may 
be obtained by synthesis by the action of ammonia on chlor- 
ethylsulphurous acid or on silver chlorethylsulphite. The fol- 
lowing formula; indicate the relations between isethionic and 
chlorethylsulphurous acids and taurine : 

c'"'<s".oii c'«*<so-'.OH cniKl'o'fon 

Isethionic acui. Chlorethylsulphurous acul. Taurine. 

Taurine crystallizes in large, brilliant, oblique rhombic prisms, 
very soluble in boiling water and but slightly soluble in cold 
water. When the crystals are heated they melt, and decompose 
at an elevated temperature. 

Strecker has obtained an isomeride of taurine by heating 
ammonium isethionate. 

c^"*<so'(NH.) = ^■'^'<Z.mP + H^o 

Ammouium isethionate. Isethionamide. 

PROPYLGLYCOLS. 
C3H6(OH)2 

Normal iwopylglycol (page 522) has been obtained from 
normal propylene bromide (page 518). This bromide is mixed 
with acetic acid and heated with silver acetate : propylene di- 
acetate is formed, C'^H''(C'^H'^0"^)^ and separated by distillation, 
after which it is decomposed by a quantity of dry potassium 
hydrate just sufficient to remove its acetic acid. 

Normal propylglycol is a colorless, syrupy liquid, boiling at 
216^, and having a density of 1.0652 at 0°. It is miscible 
with water and alcohol in all proportions. When oxidized, it 
yields hydracrylic acid (G-eromont, Reboul). 

Ordinary 'propylglycol is prepared from ordinary propylene 
bromide by the same process indicated above. It is a thick, 
colorless liquid, having a density of 1.051 at 0°. It boils at 
188-189°. When diluted with water and mixed with plati- 
num black, it absorbs oxygen, and is converted into lactic acid 
(A. Wurtz) 

GLYCERIN. 

C3H803 = C3H5(OH)3 

Glycerin was discovered by Scheele in 1799, and studied by 
Chevreul, Pelouze, and especially by Berthelot, who demon- 
strated its character of a triatomic alcohol. 
X 45 



530 ELEMENTS OP MODERN CHEMISTRY. 

Pelouze and Gelis realized the first artificial formation of a 
fjxtty body by passing hydrochloric acid gas into a mixture of 
butyric acid and glycerin : butyrin was thus produced. 

Preparation. — Gllycerin is an accessory product in the man- 
ufiicture of lead plaster. When the preparation of that sub- 
stance is terminated, the water is decanted from the lead soap 
which separates, and hydrogen sulphide is passed through the 
liquid in order to precipitate as sulphide any traces of lead that 
may be dissolved. It is then filtered and evaporated on a 
water-bath. The glycerin remains as a colorless, syrupy liquid. 

It is obtained in large quantities in the arts as an accessory 
product in the manufiicture of stearin candles. 

Properties. — Glycerin is a colorless liquid, having a syrupy 
consistence and a sweet taste. Its denstity at 15° is 1.28. It 
dissolves in all proportions in water and alcohol, but is almost 
insoluble in ether. When quickl}^ heated, it distils between 
275 and 280° ; and it may be readily distilled in a vacuum. 

Pure glycerin is crystallizable, and solidifies below 0°, but 
solid glycerin melts only at 7 or 8° (Gladstone). 

When subjected to the action of dilute nitric acid, glycerin 
is converted into a triatomic acid, which is called glyceric acid 
(Debus, Socoloff"). 

C^H«0^ -\- 0' = WO -f- e^H^o* 

Glj'cerin. Glyceric acid. 

When glycerin is poured drop by drop into a mixture of 
concentrated nitric and sulphuric acids, cooled in a vessel of 
cold water, oily drops of tyinitrogli/cerin^ C''H^(0-NO'')^, are 
precipitated. It is a yellowish oil, which explodes with gTcat 
violence by percussion, by heat, or sometimes even sponta- 
neously. 

On account of this property, nitroglycerin is employed as an 
explosive ; but it is generally incorporated with inert matter, 
such as finely-divided silica. Such mixtures are called di/na- 
mites. 

When heated with phosphorus iodide, P'-'P, glycerin is con- 
verted into allyl iodide (Berthelot and de Luca) (page 478). 

ETHERS OF GLYCERIN. 

Glycerin, C^H\OH)^ which contains three groups OH, can 
form three classes of ethers by the substitution of one, two, or 
three monobasic acid radicals lor as many atoms of hydrogen 



ETHERS OF GLYCERIN. 531 

in these hydroxyl groups. If acetic acid be heated with 
glycerin, according to the proportions of the mixture, three 
different acetic ethers of glycerin may be obtained, ethers which 
Berthelot has designated as acetuis. 

,r fOH ,„ fO.C^IPO 

C2H30.0II + C3II5 J Oil = wo + C3J15^0II 

(oh [oh 

Acetic acid. Glycerin. Moiiacctin. 

OH ,,, ro.cfH^o 

2(C2H30.0H) + C3H5 \ OH = 2H20 + C3H5 \ O.C2H30 



;3H5 \ ( 



on I OH 

Diacetin. 

,„ rOH ,„ rO.C2H30 

3(C2H30.0H) + C3H5 J OH = 3H20 + CSH^J O.C2H30 
[oh (O.C2H30 

Triacetin. 

In the same manner, by the action of the hydracids upon 
glycerin, neutral combinations are formed, analogous to the 
chlorides of the radicals C"H^""^\ as well as to the dichlo- 
ride of ethylene and to ethylene chlorhydrate. These com- 
pounds are formed by the substitution of one, two, or three 
atoms of chlorine or bromine for as many hydroxyl groups in 
glycerin. 

,n fOH „, rci 

C3H5 \ OH + HCl = C3H5 \ OH + H20 

(oh (oh 

Monoclilorhydrin. 
,n roH ,„ fCl 

c3h5 \ oh + 2hc1 = c3h5 \ ci + 2h20 
(oh (oh 

Dichlorhydrin. 

MonocTilorhydrin is a thick, colorless liquid, soluble in water 
and alcohol, and sensibly soluble in ether. It boils at 227°. 

Dichlorhydrin is a neutral, oily liquid, having a pronounced, 
ethereal odor. It dissolves in ether. Its density is 1.137, and 
it boils at 178°. 

AVhen dichlorhydrin is treated with a concentrated solution 

of potassium hydrate, the elements of hydrochloric acid are 

removed and a body is obtained which Berthelot has named 

epichlorhy drill. 

CH2C1 

C3H5C12(OH) — HCl = C3H5C10 = CH ^^ 

CH2 
Dichlorhydrin. Epichlorhydrin. 



532 ELEMENTS OP MODERN CHEMISTRY. 

Epichlorhydrin is a mobile liquid, heavier than water, and 
having an agreeable, ethereal odor. Its taste is at first sweet, 
afterwards sharp and burning. It boils at 118-119°. It is 
soluble in all proportions in alcohol and ether, but not in water. 

It combines directly with hydrochloric acid, regenerating 
dichlorhydrin. When heated for a long time with water, it 
combines with one molecule of that liquid, forming monochlor- 
hydrin. 

C^H^CIO + H^O = a^H^Cl(0H)2 

When dichlorhydrin is heated with phosphorus pentachlo- 
ride, the last hydroxyl group is removed, being replaced by 
chlorine ; tricMorhi/driii is thus obtained, 
rci rci 

CHV> \ CI + PC15 = C3H5 \ CI + P0C13 + HCl 
(oh (CI 

Dichlorhydrin. Trichlorhydrin. 

Berthelot has obtained a great number of glycerin ethers by 
directly heating glycerin with acids. When the reaction is 
terminated (it is often very slow), he saturates the excess of 
acid with calcium hydrate, and extracts the neutral fatty body, 
that is, the ether of glycerin, with ether. 

NATURAL FATTY BODIES. 

The fats encountered in nature are glycerides^ that is, ethers 
of glycerin. The memorable researches of Chevreul have 
shown that when these ftits are methodically treated with 
different solvents, various immediate principles are separated, 
of which the most common are stearin, margarin, and olein. 

They are the tristearic, trimargaric^ and trioleic ethers of 
glycerin. 

fO.Ci«H:«0 rO.Ci7H330 ro.cisH^so 

C3H5 \ O.C18H350 Q,nv> \ o.ci'H^^o C3n5 \ o.cmi^-^o 

{ O.C18H350 ( 0.01^330 ( 0.C18H330 

stearin. Margarin. Olein. 

When these glycerin ethers are subjected to the action of 
alkalies, lime, or oxide of lead, in presence of boiling water, 
they are decomposed, absorbing at the same time the elements 
of water : glycerin and the acid are set free, and the latter 
combines with the base forming a soap (see page 53-1). Thus, 
when stearin is boiled with milk of lime, calcium stearate and 
glycerin are formed. When olein is heated with water and 
litharge, it yields lead oleate and glycerin. 

Most of the natural fats are mixtures of these principles 



NATURAL FATTY BODIES. 533 

in various proportions, and to the number we may add tri- 
palmitin. 

Stearin, margarin, and palmitin arc solids, olein is liquid. 
In the fats, the solid principles predominate ; the oils contain 
a larger proportion of olein. 

Stearin is extracted from tallow. That substance is dissolved 
in boiling ether and made to crystallize. The crystals are 
pressed, and the operation is repeated with them many times 
until a substance is obtained which crystallizes in brilliant little 
scales, fusible at 60.5°. They are but slightly soluble in alco- 
hol and in cold ether, but freely soluble in boiling ether. 

Palmitin has been extracted, by the aid of boiling alcohol, 
from palm-oil which has previously been submitted to heavy 
pressure between sheets of porous paper. It melts at 60° 
(Heintz). 

Olein is the predominating principle of olive-oil and almond- 
oil, from which it is difficult to obtain it in a pure state. Ber- 
thelot has prepared triolein artificially by heating glycerin to 
a temperature between 200 and 2^0° with an excess of oleic 
acid. The mass thus obtained is treated with lime and ether ; 
the latter dissolves the triolein and leaves calcium oleate. 
The ethereal solution is decolorized with animal charcoal and 
mixed with eight times its volume of alcohol, which precip- 
itates the triolein. AVhen dried in a vacuum, triolein is an oil 
which solidifies at 10°. Its density is between 0.90 and 0.92. 
It is insoluble in water, and very slightly soluble in alcohol. 

In contact with mercuric nitrate or with peroxide of nitrogen 
(red vapors), olein is converted into a crystalline, solid, fatty 
body, fusible at 32°, to which Boudet has given the name 
elaidin. 

Fat Oils and Drying^ Oils. — The oils of olives, sweet 
almonds, rape-seed, beech-nuts, etc., acquire an acrid taste and 
a disagreeable odor when they are long exposed to the air, but 
they do not solidify. They are called fat, or non-siccative 
oils. 

Olive-oil is the type of this class. It is extracted by press- 
ure from crushed olives, and has a greenish-yellow color ; its 
taste is sweet and agreeable ; it is odorless. At a temperature 
a few degrees above 0°, it becomes a solid mass. When agitated 
with mercurous nitrate, it becomes solid, the olein which it 
contains being transformed into elaidin. It becomes rancid by 
exposure to the air. 

45* 



534 ELEMENTS OP MODERN CHEMISTRY. 

When other oils, such as linseed, walnut, hemp-seed, poppy 
and castor oils are exposed to the air, they thicken and finally 
are converted into somewhat elastic, yellow, transparent masses, 
species of soft varnishes. They are, therefore, called drying 
oils, and are employed in the preparation of paints and varnishes. 

The changes which oils undergo on contact with the air are 
caused by an absorption of oxygen, and are accompanied by a 
disengagement of more or less carbon dioxide. Every one is 
ftimiliar with the uses of the natural fatty bodies in the arts 
and in domestic economy. Among the industrial applications, 
we can only mention the employment of tallow and palm-oil in 
the manufacture of candles, and certain other oils in the fabri- 
cation of soaps. 

Stearin Candles. — To convert tallow into stearin candles, it 
is saponified by lime, that is, it is first converted into a lime 
soap, which is then decomposed by sulphuric acid. The latter 
acid causes the fatty acids to separate, and they solidify on 
cooling. They are strongly compressed, first between warm, 
and finally between hot plates, so that the oleic acid is ex- 
pressed, while the fatty acids proper remain. This process, 
which was invented by de Milly and Motard in 1829, consists, 
as may be seen, in entirely saponifying the tallow by lime. In 
1854, de Milly modified it by considerably reducing the amount 
of lime, and consequently the proportion of sulphuric acid 
required. But it is then necessary to operate at higher tem- 
peratures by the aid of superheated steam. The operation is 
conducted in closed vessels, and with 2.5 parts of lime, 100 
parts of tallow may be saponified at a temperature of 170 or 
180°. 

Palm-oil may be converted into candles by a still more 
simple process, which consists in subjecting it to the action 
of superheated steam at 300°. It is thus directly decom- 
posed into fatty acids and glycerin, for the vapor of water, 
at the high temperature employed, acts precisely as would an 
alkali. 

Soaps. — In the south of Europe, and principally at Mar- 
seilles, oils of inferior quality are used for the manufacture of 
soap, and the oils of sesame and earth-nut have been employed 
for this purpose for some years. These oils are saponified by 
boiling them in large boilers with a weak solution of caustic 
soda. The oil thus becomes pasty, the excess of oil making an 
emulsion with the solution of soap which is first formed. 



SOAP. 535 

More concentrated soda lye containinii; common salt is then 
added, and the saponification is finished by boiling ; the soap, 
which is insoluble in the concentrated lye, comes to the surface 
of the liquid, and the lye is then drawn off. When the soap 
is well made, the paste hardens on cooling ; it has a bluish-gray 
color, due to a ferruginous soap mixed with sulphide of iron. 
The iron and sulphur are derived from the materials employed, 
crude caustic soda containing a small quantity of iron. If this 
paste be heated with about one-twelfth its weight of water, or 
a very weak solution of caustic soda, it melts, and if the mass 
be allowed to stand undisturbed, it will separate into two por- 
tions, the lower and strongly-colored layer containing the more 
dense ferruginous soap ; the upper layer constitutes white soap. 
When the latter is completely clarified by the deposit of the 
ferruginous soap, it is drawn off into large moulds, where it solid- 
ifies. White soap is thus obtained. If, on the contrary, mar- 
bled soap be desired, the paste is frequently agitated during the 
cooling. The colored part, that is, the ferruginous soap, thus be- 
comes diffused throughout the whole mass, forming bluish veins. 

For some years, large quantities of soap have been prepared 
by combining with caustic soda the oleic acid obtained as an 
accessory product in the manufacture of stearin candles. 

Soft soaps have potassa for their base. They are manufac- 
tured from various oils, such as hemp, poppy, and linseed oils, 
which are saponified by caustic potassa lye. 

Saponification. — It will have been noticed that all of these 
industrial operations have for their object the decomposition 
of neutral fats into fatty acids, either free or combined with 
a base. This decomposition has received the name saponifi- 
cation. It may be effected by the action of water and heat 
alone, by the action of a base, or by the action of a powerful 
acid, such as sulphuric acid (sulphuric saponification). In the 
latter case, the acid acts upon the glycerin, forming a sulpho- 
gly eerie acid. Whatever process be employed to effect this 
decomposition, the presence of water is always necessary, for 
the elements of that liquid combine directly with the fatty 
body which is decomposed, as Chevreul has very well shown. 
In this respect, the decomposition of palmitin by superheated 
steam may serve as a type for all reactions of this class. 

fO.CiGH3io fOH 

C3H5 \ O.C16H310 + 3H20 = C3H5 \ OH + 3Ci6H3iO.OH 
[ O.C16H310 i OH 

Palmitin. Glycerin. Palmitic acid. 



536 



ELEMENTS OF MODERN CHEMISTRY. 



POLYATOMIC AND POLYBASIC ACIDS. 

These acids are related to the polyatomic alcohols, just as 
the acids containing two atoms of oxygen, and which we have 
already studied, are related to the monatomic alcohols. 

The polyatomic acids are classed in several series, among 
which we must consider in a special manner those which in- 
clude glycollic and oxalic acids. As we have already seen, 
these two acids are products of the direct oxidation of glycol. 

Theii* homologues are related to the superior glycols. 

Glycols. Acids, CnH-2n03. Acids, CnH^nj^Qi. 

CH2.0H CH2.0H CO.OH 



CH2.0H 

Glycol, 

CH2.0H 


CO.OH 
Glycollic acid. 
CH2.0H 


CO.OH 

Oxalic acid. 

CO.OH 


CH2 


CH2 


CH2 


CH2.0H 

Normal propylglycol. 
CH3 


CO.OH 
Uydracrylic acid. 
CH3 


CO.OH 
Malonic acid. 


CH.OH 


CH.OH 




Cn2.0H CO.OH 
Isopropylglycol. Lactic acid of foi mentation. 

cn2.0H 


CO.OH 


CI12 




CH2 


CH2 




CH2 


CH2.0H 

Normal butylglycol. 




CO.OH 
Succinic acid. 



The first of the above series is that of glycol and the supe- 
rior glycols. Among the latter, the true homologues of glycol 
would be those which differ from the latter by nCH'-, and of 
which the formuhis would consequently be analogous to that 
of normal propylglycol. Ordinary propylglycol, which yields 
lactic acid by oxidation, is an isomeride of normal propylglycol. 

The second series is that of glycollic acid and its homologues. 
They are derived from the corresponding glycols by the sub- 
stitution of for H^ in one group, CHIOH They conse- 
quently contain but one carboxyl group, CO.OH ; they are 
monobasic, for the hydrogen atom of the last group can be 
replaced by a metal. It will also be noticed that they are at 
the same time acids and alcohols, — acids by virtue of tlie carb- 
oxyl, CO.OH, primary alcohols by virtue of the group CH'-.OH, 
or secondary alcohols by virtue of the group CH.OH. 



GLYCOLLIC ACID. 537 

The third series is that of oxalic acid and its homologues. 
They are derived from the glycols by substitution of 0' for 
211- in two groups, CH^Oli. They conse(juently contain two 
carboxyl groups, CO.OIl, and they are dibasic because the 
H of each of these groups may be replaced by an equivalent 
quantity of metal. 

Between glycollic and oxalic acids there exists a remarkable 
acid, because it is at the same time a monobasic acid and an 
aldehyde : it is ghjoxyVic acid. It contains C'^Il'^O'^ one more 
atom of oxygen than oxalic aldehyde, which is called glijoxaJ^ 
C^H'^0'^, and two atoms of hydrogen less than glycollic acid. 
These relations of composition will be clearly seen from the fol- 
lowing formulae : 

CH2.0H Clio Clio CO.OIl 

CO.OH CO.OH CHO CO.OIl 

Glycollic acid. Glyoxylic acid. Glyoxal. Oxalic acid. 

Of all the acids which make up these series, we can only 
consider glycollic and lactic acids, which are members of the 
first, and oxalic and succinic acids, which belong to the second. 
Besides these, we will briefly describe the intermediate com- 
pounds, glyoxylic acid and glyoxal. 

GLYCOLLIC ACID. 

C2H*03= CH2(0H)-C0.0H 

This acid is formed by the oxidation of glycol. Strecker 
and Socoloff discovered it in the product of the reaction of 
nitrous anhydride upon glycocol, or sugar of gelatine (see page 
545). 

R. Hoifmann and Kekule have shown that it is produced by 
the action of an excess of potassium hydrate on monochlor- 
acetic acid. 

KC^H^CIO^ + KOH = KCl + KC^H^O^ 

Potassium monochloracetate. Potassium glycoUate. 

When pure, this acid forms deliquescent crystals, which are 
very soluble in water. It dissolves also in alcohol and in ether. 
It has a strong acid reaction. When heated, it loses the ele- 
ments of water, and is converted into glycollide^ or glycollic 
anhydride, C'H'^0^ or C^H^O*. 

C^H^O^' — H^O = C^ffO^ 

Glycollic acid. Glycollide. 



538 ELEMENTS OF MODERN CHEMISTRY. 



GLYOXYLIC ACID AND GLYOXAL. 

Glyoxylic acid is formed by the action of dilute nitric acid 
on alcohol. It may be prepared by pouring- into a tall jar, 
by means of a funnel-tube, alcohol of 80 per cent., water, and 
fuming nitric acid, successively, so that the layers may not mix 
at once. The whole is then left for about a week at a temp- 
erature of 20°, so that the three layers may gradually mix by 
diffusion. Gases are disengaged, and the product contains nitric 
acid, glyoxylic and glycollic acids, several ethers and aldehydes, 
and notably glyoxal. The liquid is distributed in flat plates 
and evaporated to a syrupy consistence on a water-bath. The 
residue is exhausted with water, neutralized with chalk, and fil- 
tered. Alcohol is added to the filtered liquid, and precipitates 
glyoxylate and glycollate of calcium. The alcoholic mother- 
liquor contains glyoxal. The precipitate of calcium salts is 
collected on a filter, pressed, and dissolved in boiling water. 
The solution being allowed to evaporate spontaneously, the cal- 
cium glyoxylate, which is least soluble, is deposited first. Gly- 
oxylic acid may be isolated by decomposing an aqueous solution 
of calcium glyoxylate by oxalic acid. 

Glyoxylic acid is a syrupy and very acid liquid. Its consti- 
tution shows it to be at the same time an acid and an aldehyde, 

PTTO 
and this double function is expressed by the formula i 

CO.OH 
Its solution reduces ammoniacal silver nitrate. When heated 
with sulphuric acid it disengages carbon monoxide. 
C^ffO^^ = 2C0 4- H^O 

Nascent hydrogen converts it into glycollic acid. 

Q2JJ2Q3 _|_ H^ .= C^H^O^ 

Glyoxal. — This body is formed at the same time as the pro- 
ducts above mentioned, by the action of weak nitric acid on 
alcohol. It is prepared from the alcoholic solution which sepa- 
rates from the calcium glycollate and glyoxylate. To this is 
added a concentrated solution of sodium acid-sulphite, which 
forms a crystalline combination with the glyoxal. This com- 
bination deposits and is collected, purified by recrystallization 
in water, and barium chloride is added to its aqueous solution. 
A sulphite of glyoxal-barium is formed by double decomposi- 
tion, and deposits in crystalline crusts. To it^ solution in boil- 



LACTIC AND PARALACTIC ACIDS. 530 

inp; wiitor sulphuric acid is added in quantity exactly sufficient 

to preeipitate the barium as sulphate. The filtered li(juid will 

contain sulphurous acid and gl^'oxal, and the latter alone will 

remain alter evaporation on a water-bath. 

Glyoxal is a deli([uescent, amorphous solid, sli<ihtly colored, 

and very soluble in water and alcohol. Its aqueous solution 

energeticall}^ reduces ammonio-nitratc of silver. It combines 

with the acid-sulphites, like the other aldehydes. Glyoxal is 

the aldehyde corresponding to oxalic acid. 

Clio CO.OII 

Clio CO.OH 

Glyoxal. Oxalic acid. 

LACTIC AND PARALACTIC ACIDS. 

C3U603 = CH3-CH(0H)-C0.0H 

Formation and Constitution. — Lactic acid was discovered 
by Scheele in sour milk. Berzelius discovered the existence in 
various liquids of the animal economy of an acid which was at 
first believed to be identical with that wdiicli results from the 
acid fermentation of milk. Later, an acid identical with the 
latter was found in various vegetable juices, and was recog- 
nized to be the product of a peculiar fermentation of glucose, 
called the lactic fermentation. It was also discovered that 
the lactic acid of fermentation is not identical with that which 
exists in the animal liquids, especially that liquid which im- 
pregnates the muscular fibres. The latter acid is called para- 
lactic acid. The nature of its isomerism with lactic acid has 
been recently discovered by Wislicenus. It is a case of phys- 
ical isomerism ; paralactic acid is optically active, and this 
physical peculiarity carries in its train slight modifications in 
chemical properties ; these variations will be indicated when 
treating of the lactates. 

Independently of the acids which have just been mentioned, 
there is another which was at first named ethylene-lactic acid, 
and which results from the oxidation of normal propylglycol ; 
its constitution is expressed by the formula 

CH2.0H 

CH2 

CO.OH 
It is liydracryllc add; it is also formed when /9-iodopropi- 
onic acid is treated with water and silver oxide. Its character- 



540 ELEMENTS OF MODERN CHEMISTRY. 

istic property is its easy decomposition into water and acrylic 
acid, hence the name hydracryHc (Wislicenus). 

Its isomeride, lactic acid of fermentation, is formed by the 
oxidation of ordinary propyliilycol (A. Wurtz). This fact 
determines its constitution, which can also be deduced from 
a very interesting mode of formation discovered by Strecker. 
When a mixture of aldehyde, hydrocyanic acid, and hydro- 
chloric acid is allowed to stand for some time, ammonium chlo- 
ride and lactic acid are formed. 

CH3 

^^' + CNH + HCl + 2n20 = NH^Cl + CH.OH 

^^^ CO.OH 

Aldehyde. Hydrocyanic Lactic acid, 

acid. 

The isomerism of lactic and hydracrylic acids may be readily 

understood by the aid of the following formulae : 

CH2.0H CH3 

CH2 CH.OH 

CO.OH CO.OH 

Hydracrylic acid. Lactic acid. 

Both acids are monobasic ; each contains the group CO.OH, 
which is characteristic of organic acids. The third ox3^gen 
atom exists in alcoholic hydroxyl, either in the primary group 
CH'-.OH, or in the secondary group CH.OH. 

The preceding formulas show that lactic acid has a mixed 
function ; it is at the same time an alcohol and an acid. This 
is made evident in all of its compounds, and it will be sufficient 
to mention that one molecule of lactic acid in its function as 
an acid^ can react with and etherify another molecule in its 
function of an alcohol^ the hydroxyl of the group CO.OH 
forming a molecule of water with the hydrogen of the alco- 
holic hydroxyl in the second molecule of the acid. The 
dilactic acid, lactic anhydride, and lactide which are formed by 
the more or less complete dehydration of two molecules of 
lactic acid, are veritable dilactic ethers. This point has been 
developed by Grimaux. 

Preparation of Lactic Acid. — A mixture of 3 kilo- 
grammes of glucose dissolved in 13 litres of water, 4 kilo- 
grammes of sour milk, 100 grammes of old cheese, and 1.5 
kilogrammes of pulverized chalk, is exposed to a temperature 
of 30 or 35°. At the end of a week, the whole solidifies to 



PARALACTIC ACID. 541 

a miiss of calcium lactate. The salt is purified by crystal- 
lization, and is exactly decomposed by dilute sulphuric acid. 
The calcium sulphate is separated by filtration, and the acid 
liquid is boiled and saturated with hydrocarbonate of zinc ; 
It is then filtered and allowed to cool. The zinc lactate crys- 
tallizes, and its solution being decomposed by hydrogen sul- 
phide, zinc sulphide and lactic acid are obtained. The latter is 
separated by filtration and its solution concentrated on a water- 
bath. 

Properties. — Lactic acid is a colorless, syrupy liquid, having 
a decided acid taste. When heated, it begins to lose water at 
130°, and is converted, little by little, into a yellow, amorphous 
mass, insoluble in water, but soluble in alcohol and ether. This 
body is dilactic acid, C*^H'°0^ 

At 230°, it disengages a small quantity of carbon monoxide 
and carbon dioxide, and a product distils which often solidifies 
on cooling. It is lactide^ or dilactic anhydride, and is derived 
directly from dilactic acid. 

C6JJ10Q3 ^ C^H^O* + H'O 

Dilactic acid. Lactide. 

Lactide has been represented by the more simple formula 
C^H^O', but L. Henry has shown by a determination of vapor 
density that the double formula represents the true constitution 
of this body. Grimaux had already arrived at the same con- 
clusion from theoretical considerations. 

Lactide occurs in colorless crystals, soluble in water and 
alcohol. It possesses the property of combining directly with 
the elements of water, lactic acid being reformed ; it also com- 
bines with ammonia, forming lactamide. 

Faralactic Acid. — This is the lactic acid which may be 
extracted from meat. It is also called sarcolactic acid. It may 
be prepared from commercial extract of meat ; this is dissolved 
in 4 parts of water, and the solution precipitated by 8 parts 
of 90 per cent, alcohol. The alcoholic solution is decanted, 
and the residue, which is insoluble in alcohol, is exhausted with 
2 parts of lukewarm water, the solution again being precip- 
itated by alcohol. The alcoholic solutions are united and dis- 
tilled on a water-bath. The residue is rendered strongly acid 
by sulphurous acid, and agitated with ether which dissolves the 

46 



542 ELEMENTS OF MODERN CHEMISTRY. 

paralactic acid set free. The ethereal solution is evaporated, 
and the acid is converted into the salt of zinc, which is subse- 
quently decomposed by hydrogen sulphide, as has been indicated 
for the preparation of ordinary lactic acid. Paralactic acid is 
syrupy like its isomeride. It turns the plane of polarized light 
to the right (Wislicenus). When heated, it becomes dehy- 
drated, yielding lactide. 

According to Wislicenus, extract of meat contains still an- 
other paralactic acid, isomeric with the preceding, but optically 
inactive. 

Lactates and Paralactates. — Lactic acid is a monobasic 
acid; the neutral lactates contain li'C'H^O^ or M"(0^H50')^ 
The most characteristic is zinc lactate^ Zn(C^H^O^/^ -(- 3H'^0, 
which is but slightly soluble in cold water, and separates from 
its boiling solution in brilliant needles or lamina?. 

Zinc i^aralactate crystallizes with two molecules of water, 
and is much more soluble than the ordinary lactate. 

Calcium lactate, Ca(C'H50'/' + 5H'0, crystallizes in 
rounded masses, formed of little needles grouped around a 
common centre. Like all the lactates, it is very soluble in 
water and alcohol. Its isomeride, calcium i^aralactate, is 
deposited from boiling water with 4 molecules of water of 
crystallization. According to Wislicenus, this salt contains 
2[Ca(C=^H^O^)2] -f OH^O. 

Ferrous lactate, Fe(C^H^O^)^ prepared by double decompo- 
sition of calcium lactate and ferrous sulphate, forms greenish, 
crystalline crusts, soluble in water. It is employed in medicine. 

Lactamide, C'H^NO^ — When an alcoholic solution of lac- 
tide is treated with ammonia and the liquid is evaporated, 
crystals are obtained which are soluble in water and alcohol. 
They constitute lactamide. 

Q'WO' + 2NH^ ^-- 2C^H^N0^ 

Potassium hydrate decomposes lactamide into lactic acid and 
ammonia. 

Lactamide represents ammonium lactate less the elements 
of water. 

CH.OH — H20 = CH.OH 

C0.0(NH4) C0.NH2 

Ammonium lactate Lactamide. 



HYDRACllYLIC ACID. 543 



HYDRACRYLIC ACID. 

(etiiylenelactic, or ethenelactic acid.) 
C3H603 = CH'^(0H)-CH2-C0.0H 

This acid is formed by the oxidation of normal propylglycol. 
It is also formed by the action of water and silver oxide on 
/5-iodopropionic acid. 

CH2I-CH2-CO'^H + AgOH- = CH'''.OH-CH'^-CO.OH -f Agl 

^-lofiopropionic acid. Hydracrylic acid. 

The silver salt formed in the latter reaction is converted into 
the zinc salt, and the latter is decomposed by hydrogen sul- 
phide. 

Hydracrylic acid is syrupy. When heated, it breaks up 
into acrylic acid and water. 

C3JJ6Q3 ^ c^^H^O- -f H^O 

When heated with hydriodic acid, it is again converted into 
/?-iodopropionic acid. Its sodium salt, NaC'MPO'^ deposits from 
alcohol in crystals fusible at 142-143°. Between 180 and 200°, 
it loses water, and is partly converted into sodium acrylate. 

Zinc Jii/draoylate, Zn(C^H^O'')^ -|- H'^0, is characteristic. 
It forms large, very brilliant crystals, soluble in about one part 
of water. 



GLYCERIC ACID. 
C3H60* == CH2(0H)-CH(0H)— CO.OH 

This acid is obtained by oxidizing glycerin with nitric acid, 
or by treating it with bromine and water. It is also formed 
by the spontaneous decomposition of nitroglycerin. 

It is prepared by introducing into a tall jar one part of nitric 
acid of specific gravity 1.5, and 1 part of glycerin diluted with 
its own volume of water. Care is taken that the two liquids may 
not mix, and the whole is left to itself for five or six days. The 
two bodies gradually mingle and react upon each other. The 
liquid is evaporated on a water-bath, and the residue is boiled 
with well-washed hydrate of lead suspended in water, after 
which the solution of lead-salt is filtered hot. Crystals of lead 

* Instead of Ag20 + H20. 



544 ELEMENTS OF MODERN CHEMISTRY. 

glycerate separate on cooling; they are purified, and their 
af(ueous solution when decomposed by hydrogen sulphide, fur- 
nishes glyceric acid. 

Properties. — G-lyceric acid is a thick, light-yellow syrup, 
soluble in water and alcohol. Its reaction is acid ; it is mono- 
basic, llydriodic acid, by the aid of heat, converts it into 
/J-iodopropionic acid. Its relations with glycerin may be seen 
in the following formulae : 



CIROH 


CO.OII 


CH.OH 


CH.OH 


CH2.0H 
Glyceiia. 


CH2 0H 
Glyceric acid. 



Closely related to glycollic and lactic acids are two important 
nitrogenized bodies, glycocol and alanine. They form part of 
a series which includes among other bodies leucine, a nitro- 
genized compound which plays a part in the animal economy. 

When a current of nitrous anhydride is passed into solutions 
of glycocol, alanine, and leucine, nitrogen is disengaged, and 
these bodies are converted into glycollic, lactic, and leucic acids. 
We then have the following series : 

Glycollic acid. Glycocol. 

Lactic acid. Alanine. 

Leucic acid. Leucine. 

GLYCOCOL. 

C2H5N02 = CH2(NH2)-CO OH 

This body is related to glycollic acid. It was discovered by 
Braconnot, who obtained it by boiling gelatin with dilute sul- 
phuric acid for a long time, saturating the solution with barium 
carbonate and evaporating the filtered liquid. Hence the name 
sugar of gelatin or glycocol. 

Cahours obtained it by the action of ammonia on mono- 
chloracetic acid. 

?0-''« + 2NII3 = NH.C1 + f°0" 
CH^Cl CH2.Nn2 

Monochloracetic acid. Glycocol. 

It is therefore amidacetic or acetamic acid. 



ALANINE. 545 

It is a solid body, crystallizing in oblique rhombic prisms, 
fusible at 170^. Its taste is sweet. It is soluble in water, 
slightly soluble in alcohol, insoluble in ether. Its solution has 
a feeble acid reaction. Indeed, glycocol can react with the 
bases, forming compounds; when it is digested for several hours 
at a temperature between 80 and 104° with silver oxide, the 
latter is dissolved, and the compound C'^H'AgNO'^ is formed. 
On the other hand, glycocol will combine with the acids; there 
is a crystallizable nitrate of glycocol. 

When nitrous anhydride is passed into a solution of glycocol, 
the latter is converted into glycollic acid, nitrogen being at the 
same time disengaged. 

2C-IPN0^ + N^O^ = 2C^irO^ + H^O + 2N2 

Glycocol. Glycollic acid. 

ALANINE. 

C3H7N02 == CH3-CH(NH'!)-C0.0H 

Strecker made the synthesis of alanine by passing hydro- 
chloric acid gas into a mixture of aldehyde-ammonia and hydro- 
cyanic acid. 

C^H^O + CNH + H^O =■- en^NO^ 

The brown liquid resulting from this reaction is evaporated. 
Alanine crystallizes in hard needles, grouped in stars or tufts. 
It is soluble in water, only slightly soluble in alcohol, insoluble 
in ether. The aqueous solution is neutral, and is converted 
by nitrous anhydride into lactic acid, with evolution of nitrogen. 

2C^H"N0' + N^O^ = 2C'H«0^ + WO + 2W 

Alanine. T actic acid. 

Alanine may be sublimed by cautiously heating it. By dry 
distillation, it breaks up into carbon dioxide and ethylamine. 

C^H^NO^ = CO^ + C^H^NH^ 

It is isomeric with lactamide and with an acid amide which 
is obtained by the action of ammonia on /?-iodopropionic acid. 
The following formulae account for these isomerides : 



CH3 


CH2.NH2 


CH3 


CH.OH 


CH2 


CH.NH2 


C0.XH2 
Lactamide. 


CO.OH 

^-amidupropionic acid. 

46* 


CO.OH 
Alanine. 



546 ELEMENTS OF MODERN CHEMISTRY. 

/?-amidopropionic acid, which is formed in the reaction just 
indicated, crystallizes in transparent and colorless oblique 
rhombic prisms. It is very soluble in water and but slightly 
soluble in alcohol. When cautiously heated to 170°, it partly 
sublimes in needles. 

LEUCINE. 

C6H13N02 

This body was discovered by Proust, in 1818^ in old cheese. 
It seems to be identical with a substance obtained from cadav- 
eric fat, and named by Fourcro}^ apose2'>edine. It is a product 
of the putrefaction of animal matters. It is also formed when 
horn, gelatinous tissues, or albuminous matters are boiled with 
dilute sulphuric acid, or fused with potassium hydrate. In 
these reactions, tyrosine, and sometimes glycocol, is formed at 
the same time. 

Leucine exists already formed in the economy. It is met 
with in the tissues of the liver, spleen, lungs, pancreas, and 
in the salivary glands, etc. Lim})richt has formed it artifi- 
cially, by a process analogous to that employed by Strecker for 
the synthesis of alanine. 

Preparation. — The best process for the preparation of leu- 
cine, consists in boiling for twenty-four hours 2 parts of horn- 
shavings with 5 parts of sulphuric acid and 13 parts of water, 
care being taken to replace the water as it evaporates. The 
liquid is neutralized with milk of lime, the calcium sulphate 
separated by filtration, and a small quantity of lime that re- 
mains in solution is precipitated by oxalic acid. The filtered solu- 
tion, left to itself, first deposits tyrosine, and the leucine remains 
in the mother-liquor, from which it separates in crystals on spon- 
taneous evaporation. It is finally crystallized from weak alcohol. 

Properties. — Leucine crystallizes in white plates. It dis- 
solves in 27 parts of cold water and much more abundantly in 
boiling water. It melts at 170°, and decomposes at a higher 
temperature into carbon dioxide and amylamine. 
C^H^'NO-' == CO' + C^H^.NIP 

AVhen nitrous anhydride is passed into a solution of leucine, 
it is converted into a homologue of lactic acid, leucic acid 
(Strecker). 

2C«H'='N0'' -f N^O^' = 2Cnr'-'0^ + IPO + 2N'^ 

Leucic acid. 



OXAL[C ACID. 547 

OXALIC ACID. 

C2I120* = C0(01I)-C0(0II) 

Natural State and Modes of Formation. — This important 
acid exists in many vegetables. Wiegleb and Scheele extracted 
it from salt of sorrel, which is an acid oxalate of potassium. 

The process of Scheele has become classic. It consists in 
precipitating a solution of salt of sorrel with acetate of lead, 
and decomposing the precipitated lead oxalate by hydrogen 
sulphide. The great Swedish chemist demonstrated the iden- 
tity of the acid thus formed and that which Bergman had 
anteriorly obtained by treating sugar with nitric acid. 

Oxalic acid is met with in the animal economy. Urine often 
deposits little crystals of calcium oxalate, which salt is some- 
times deposited in the bladder and there forms rough concre- 
tions known as mulberry calculi. 

Oxalic acid is formed by the action of nitric acid or fused 
potassium hydrate on a great number of organic matters. 

Cyanogen yields oxalic acid by its decomposition in contact 
with water (page 431). 

We have already studied the relations which exist between 
oxalic acid and glycol (page 524). 

Drechsel has recently made a beautiful synthesis of oxalic 
acid. By passing carbon dioxide upon sodium disseminated in 
very dry quartz sand and heated to 350^, he obtained sodium 
oxalate. 

2C0' + Na^ = Na^C'O* 

Sodium oxalate. 

Preparation. — Oxalic acid is prepared in the arts by two 
processes. One consists in the oxidation of molasses of an 
inferior quality by nitric acid. The operation gives rise to an 
abundant disengagement of nitrous vapors and carbon dioxide. 
It is conducted in leaden boilers that are not attacked in pres- 
ence of a great excess of oxidizable organic matter. 

Another process consists in the reaction of potassium hy- 
drate on saw-dust at a high temperature. The mass is ex- 
hausted with water which dissolves out potassium oxalate, and 
the solution is treated with milk of lime. Calcium oxalate is 
precipitated and potassium hydrate is reformed. The precip- 
itated calcium oxalate is decomposed by sulphuric acid, calcium 
sulphate, which is almost insoluble, being formed, and oxalic 



548 ELEMENTS OF MODERN CHEMISTRY. 

acid remaining in solution in the water. When the latter is 
sufficiently concentrated, the acid is deposited in crystals. The 
potassium hydrate which remains in the first solution is evapo- 
rated, and serves for new operations. 

Properties. — Oxalic acid crystallizes from its aqueous solu- 
tion in large, transparent prisms, containing 2 molecules of 
water. When exposed to the air, these crystals effloresce, and 
they completely lose their water at 100° or in a dry vacuum. 
One part of oxalic acid dissolves in 15.5 parts of water at 10°. 
It is also very soluble in alcohol. 

It melts in its water of crystallization at 98°; at 1.32° it 
begins to disengage gases, and between 155 and lGO°it breaks 
up into water, carbon monoxide, carbon dioxide, and formic 
acid. 

Cm'O' = QO' 4- CH^O^ 
C^H^O^ := CO^ + CO + H^O 

At the same time, a portion of the dry acid escapes decompo- 
sition and sublimes. 

When oxalic acid is heated with sulphuric acid, it is de- 
composed into carbon monoxide, carbon dioxide, and water, 
according to the equation given above. 

Certain chlorides are reduced by ebullition with a solution 
of oxalic acid : hydrochloric acid is formed, and carbon dioxide 
is disengaged. Under these circumstances, auric chloride de- 
posits metallic gold ; mercuric chloride is reduced to mercurous 
chloride. 

Oxalic acid is a violent poison. In doses of 8, 12, to 20 
grammes, it produces poisonous effects which may prove fatal. 
It acts upon the heart, retarding its movements, and upon the 
nerve centres, of which it rapidly depresses the functions. 

If a solution of oxalic acid, or better, ammonium oxalate, 
be added to a solution of calcium chloride, a white precipitate 
of calcium oxalate is formed. This precipitate is formed even 
in very dilute solutions. If a small quantity of silver oxalate 
be heated in a small test-tube, the salt decomposes suddenly 
with a slight explosion, leaving a gray powder of metallic 
silver, part of which is violently projected from the tube. 



Ag'^C'^0* = 2C0^ + Ag2 



,.2 

Silver oxalate. 



These reactions characterize oxalic acid. 

Oxalates. — Oxalic acid is dibasic. Its two atoms of hydro- 



OXAMIDE. 549 

gen may be replaced by two atoms of a univalent metal, or by 
one atom of a bivalent. Acid oxalates and neutral oxalates 
are known. 

Potassium Acid Oxalate, KIIC-'O* -f- IPO.— This salt con- 
stitutes the iiTcater part of the salt of sorrel of commerce. It 
is extracted from the juice of various kinds of Rumex and 
Oxalis, the juice of which is clarified with clay and then 
evaporated to crystallization. It is but slightly soluble in 
water. 

If a concentrated solution of oxalic acid be agitated with a 
solution of potassium neutral oxalate, a precipitate of potassium 
acid oxalate will be formed. 

If a concentrated solution of oxalic acid be agitated with 
a solution of potassium acid oxalate, a white precipitate of 
potassium quadroxalate, a combination of the acid salt and 
oxalic acid, will be deposited. It contains C'H'O* + KHC'O* 
+ 2H-'0. 

Neutral Potassium Oxalate, K-^CO* + H^O, is obtained 
by neutralizing a solution of the acid salt with potassium car- 
bonate and evaporating. It crystallizes in oblique rhombic 
prisms, very soluble in water. 

Ammonium Oxalate, (NH*)^C'0* + H'^0, which is fre- 
quently used as a reagent, is prepared by neutralizing oxalic 
acid with ammonia. The concentrated solution deposits color- 
less crystals belonging to the type of the right rhombic prism. 
There is also an acid oxalate of ammonia, (NH*)HC^O*. 

Ethyl Oxalate, or Oxalic Ether, (C^H^)^C^O*.— This ether 
may be prepared by distilling a mixture of 1 part of potassium 
acid oxalate, 1 part of alcohol, and 2 parts of concentrated 
sulphuric acid. The addition of water to the distilled liquid 
causes the separation of an oily layer which sinks and is de- 
canted. It is washed with a solution of an alkaline carbonate, 
and distilled, only that portion being retained which passes 
above 180°. Oxalic ether is a colorless liquid, heavier than 
water, and having an aromatic odor. It boils at 186°. 

OXAMIDE. 

If solution of ammonia be added to ethyl oxalate, the latter 
immediately solidifies to a white mass formed of a crystalline 
powder. This is oxamide. 



550 ELEMENTS OF MODERN CHEMISTRY. 

c'n5;o>C-0'^ + 2NII3 =^ C202<5J{}:j + 2(C2H5.01I) 
Kthyl oxalate. Oxaniide. 

Oxamide is also formed by the dry distillation of ammonium 
oxalate. 

nh':o>^'^' = c2o-2<^;{{:; + 2H20 

The latter reaction, studied in 1830 by Dumas, led to the 
discovery of the amides. 

Oxamide is a white, crystalline powder, very slightly soluble 
in cold water, insoluble in alcohol, somewhat soluble in boiling 
water, from which it is deposited on cooling. Like all of the 
amides, it is decomposed by boiling potassium hydrate, am- 
monia being disengaged and potassium oxalate formed. 

Oxamic Acid. — This body is formed when ammonium acid 
oxalate is heated to between 220 and 238° (Balard). 

Ammonium acid oxalate. Oxamic acid. 

It is a yellowish, grainy powder which boiling water again 
converts into ammonium acid oxalate by the direct addition of 
one molecule of water. 

The following formulae express clearly the relations existing 
between oxalic acid, oxamic acid, and oxamide : 

C^OKoH G'0'<:^n C202<NH^ 

Oxalic acid. Oxamic acid. Oxamide. 



SUCCINIC ACID. 

C*H60* = CO.OH-CH2-CII2-CO.OH 

This acid, which was first obtained by the distillation of 
amber, is one of the products of oxidation by nitric acid of the 
complex fatty acids, such as palmitic and stearic acids. It is 
also formed by the fermentation of calcium malate and by the 
reduction of malic and tartaric acids by hydriodic acid. 

Maxwell Simpson obtained it synthetically by decomposing 
ethylene dicyanide with potassium hydrate. 

+ 2NH3 
In this reaction the nitrogen of each cyanogen group unites 



cir-'-cN , 




CI12-C0.0TI 


1 + 


41120 = 




CII2-CN 




CH2-C0.0H 


Ethylene dicyanide. 




Succinic acid. 



SUCCINIC ACID. 551 

with IP, and is replaced by O'H = 2(H"^0) — IF. Succinic 
acid then contains two groups CO'II, combined with ethyksne. 
It is dibasie. 

Preparation. — Succinic acid may be prepared either by tlie 
dry distiUation of amber and purifying the solid product of 
this distillation, or by exposing- for some time calcium malate 
mixed with a small quantity of white cheese to a temperature 
of 30 or 40°. By a sort of fermentation the malate is then 
converted into succinate, and the calcium succinate, being de- 
composed by dilute sulphuric acid, yields calcium sulphate, 
which is separated by filtration, and a solution of succinic acid 
which crystallizes after concentration. 

Properties. — Succinic acid forms large, colorless crystals, un- 
akered by the air, and fusible at 180°. At li35° it boils and 
breaks up into succinic anhydride and water. 

Succinic acid. Succinic anhydride. 

It is quite soluble in water, less so in alcohol, and almost in- 
soluble in ether. 

When subjected to dry distillation, it loses one molecule of 
water, and is converted into succinic anhydride^ C^IFO'^, which 
forms a white, crystalline mass. The latter body is converted 
by phosphorus pentachloride into succinyl chloride, CTI^O-CP. 

Cn2-C0^ CIP-COCl 

I >0 + PC15 = P0CI3 + I 

CH2-C0^ CH2-C0CI 

Succinic anhj'dride. Succinyl chloride. 

Kekule has obtained monohromo-snccinic and dihromo-svc- 
cinic acids by heating moistened succinic acid with bromine in 
sealed tubes. 

Monobromo-succinic acid is converted into malic acid when 
treated with water and silver oxide. 

C2H3Br<^^'n + AgOH = C2H3(OH)<gg',g ^ ^^^^ 
Monobromo-succinic acid. Malic acid. 

Under the same circumstances, dibromo-succinic acid is con- 
verted into tartaric acid. 

C2H2Br2<^^2H + 2AgOH = C2H2(0H)2<^^2n + 2AgBr 
Dibromo-succinic acid. Tartaric acid. 

These reactions, which were discovered by Kekule, establish 
very close relations between succinic, malic, and tartaric acids. 



552 ELEMENTS OP MODERN CHEMISTRY. 

C^HfiQ* succinic acid. 
C*II605 malic acid. 
C*11606 tartaric acid. 

The following formulae express the constitutions of these 
acids : 

CH2-C0.0H 

6r^-co.or ---i^-«id- 

CH(OH)-CO.OH 
ilP-CO.OH ^-''^-^'^' 

CH(OH)-CO.OH 
I tartaric acid. 

CH(OH)-CO.OH 

Malic acid is oxysuccinic acid, and tartaric acid is dioxysuc- 
cinic acid. By reducing agents, the latter acids can be con- 
verted into succinic acid. When either of them is heated with 
a large excess of hydriodic acid, water is formed, iodine is de- 
posited, and the liquid will be found to contain succinic acid 
(Schmitt and Dessaignes). 



MALIC ACID. 
C*H605 = C0.0H-CH2-CH(0H)--C0.0H 

This acid, which exists in a number of vegetables, was ex- 
tracted by Scheele from apple-juice. It is generally prepared 
from the berries of the mountain-ash, gathered before their 
complete maturity ; they are strongly pressed, and the juice is 
boiled, filtered, and neutralized with milk of lime at the ordi- 
nary temperature. Calcium malate is deposited, and this is 
converted into the acid malate by dissolving it in boiling water 
acidulated with nitric acid. The calcium acid malate may be 
readily purified by crystallization, after which it is converted 
into malate of lead by double decomposition with lead acetate. 
The lead salt is suspended in pure water and decomposed by 
hydrogen sulphide ; the solution of malic acid is then filtered 
and evaporated (Liebig). 

Properties. — Malic acid crystallizes in little needles grouped 
in rounded grains. These deliquesce wdien exposed to the air. 

The aqueous solution of malic acid has a marked acid taste. 
"When long kept, it becomes filled with vegetations. It de- 
viates the plane of polarization to the left. However, there is 
an inactive malic acid which has no efi"ect on polarized light 



ASPARAGIN. 553 

(Pasteur). Solution of malic acid docs not produce a cloud in 
lime-water, neither in the cold, nor on boiling. 

When malic acid is heated, it begins to lose water at 130°, 
and between 150 and 200° is converted into two acids which 
are isomeric with each other, and are known as maleic and 
fumaric acids. 

(14^605 ^ c^H'O* + H-'O 

Malic acid. Maleic and fumaric acids. 

By the action of potassium hydrate at about 150°, malic 
acid is decomposed into oxalic and acetic acids. 

mi'O' + IPO = C^H-'O* + c-'H^o^ + H^ 

Malic acid. Oxalic acid. Acetic acid. 

ASPARAGIN AND ASPAKTIC ACID. 

Succinic and malic acids present simple and remarkable rela- 
tions with two nitrogenized bodies which have long been known ; 
they are asparagin and aspartic acids. 

The latter body is amidosuccinic acid, and bears the same 
relations to succinic acid that glycocol (amido-acetic acid) bears 
to acetic acid. On the other hand, its relations to malic acid 
are analogous to those of glycocol to glycoUic acid. 
C1I3 CIP.OH Cn2.NH2 

CO.OH CO.OH CO.OH 

Acetic acid. Glj'coUic acid. Glycucol. 

CIP-CO.Oir C0(01I)-C0.0H CH(NH2)-C0.0II 

CH2-C0.0H CIP -CO.OH CH^-CO.OH 

Succinic acid. sialic acid. Aspartic or amidosuccinic acid. 

Asparagin is the monamide of aspartic or amidosuccinic acid ; 
it is isomeric with the diamide of malic acid. 

CH(NII2)-C0.NH2 CH.0H-C0.NH2 

CH2_C0.0II CH2-C0.NII2 

Asparagin. Malamide. 

Asparag'in, C^H^N-Ol — This body exists naturally in aspa- 
ragus, black salsify, the roots of marsh-mallow, licorice wood, 
and in the buds of cereals, peas, vetches, and beans before they 
flower. To extract it from these vegetables, they are expressed 
while fresh, and the juice is clarified and concentrated. The 
asparagin is deposited in colorless crystals. It is only slightly 
soluble in cold water and alcohol, but is more soluble in hot 
water. It forms combinations with both bases and acids. 
T 47 



554 ELEMENTS OF MODERN CHEMISTRY. 

When boiled with these agents, it loses ammonia and is con- 
verted into aspartic acid. 

C*H«N'^0^ + H^O --= NIP == C^H'NO* 

Asparagin. Aspartic acid. 

Aspartic Acid, C*H^NO*, forms rhombic crystals, slightly 
soluble in cold, and more soluble in hot water. Like glycocol, 
aspartic acid can form compounds with both acids and bases. 

TARTARIC ACID. 

C4H606 _ CO.OH-CH(OII)-CH(OII)-CO.OH 

This important acid was discovered by Scheele in the tartar, 
or argol., which is deposited in casks in which wine is kept. 
It is prepared from purified tartar, called cream of tartar^ which 
is acid tartrate of potassium. 

Preparation. — The salt is dissolved in boiling water, and 
chalk is added until all effervescence, due to the disenoase- 
ment of carbon dioxide, ceases. Insoluble calcium tartrate is 
deposited, and potassium neutral tartrate remains in solution. 
The calcium tartrate is collected on a filter, and the filtrate is 
precipitated by calcium chloride. A new portion of insoluble 
calcium tartrate is thus obtained, and is washed and united with 
the first portion. This salt is then suspended in water and 
exactly decomposed by dilute sulphuric acid ; calcium sulphate 
is precipitated, and separated by filtration, and the filtered 
liquid, when sufficiently concentrated and allowed to evaporate 
in a warm place, deposits crystals of tartaric acid. 

Properties. — Tartaric acid crystallizes in large, oblique rhom- 
bic prisms, which often present hemihedral facettes. They are 
unaltered by the air, and dissolve in about half their weight 
of cold water and still more abundantly in boiling water. 
They dissolve also in alcohol, but not in ether. 

The aqueous solution of tartaric acid turns the plane of 
polarization to the right. It forms white precipitates in lime- 
water and baryta-water, but an excess of the acid redissolves 
these precipitates. 

If an excess of tartaric acid be added to a solution of cupric 
sulphate, the liquid may be saturated with potassium hydrate, 
but no precipitation of cupric hydrate will take place. The 
li(|uid will remain transparent and will assume a beautiful 
dark-blue color ; it is called cupro-potassic solution. In the 



TARTARIC ACID. 555 

same manner, ferric chloride, to which tartaric acid has been 
added, is not precipitated by an excess of potassium hydrate. 

When tartaric acid is fused with potassium hydrate, it is 
decomposed into acetic and oxaUc acids. 

Action of Heat on Tartaric Acid. — 1 . Tartaric acid fuses 
between 170 and 180°, and when the action ot the heat is not 
prolonged, it is converted into an isomeric acid, called meta- 
tartaric. 

2. If the acid be maintained for some time in fusion, it 
loses water and is converted into ditartaric acid. 

Ditartaric acid. 

3. When 15 or 20 grammes of tartaric acid are suddenly 
heated over a naked fire for four or five minutes, the mass 
swells up and a deliquescent, yellow, spongy mass is obtained, 
which constitutes what is called tartaric anhydride. 

C1JJ6Q6 ^ c*H^O^ + H^O 

Tartaric anhydride. 

When heated for some time to 150° in a hot-air oven, tar- 
taric anhydride becomes insoluble. 

4. When tartaric acid is distilled by heating it gradually in 
a retort to 300°, it is transformed into two pyrogenous acids, 
pyruvic and pyrotartaric acids. 

Pyruvic acid. 

2C*H«0'' = C^H«0* + 3C0^ + 2H^0 

Pyrotartaric acid. 

It is seen that these acids, produced by the action of heat 
on a complex organic acid, differ from the latter only by the 
elements of water and carbon dioxide. Such is the laio of 
pyrogenous acids established by Pelouze. 

When tartaric acid is heated to 170°, in sealed tubes, with 
water, it undergoes a remarkable modification : it is converted 
into paratartaric acid and inactive tartaric acid ; the latter is so 
named because it is without action on polarized light, and 
cannot be broken up, as can paratartaric acid, into a dextrogy- 
rate and a levogyrate acid ( Jungfleisch). 

Action of Nitric Acid upon Tartaric Acid. — Very con- 
centrated nitric acid converts tartaric acid into nitrotartaric 



556 ELEMENTS OF MODERN CHEMISTRY. 

acid^ C*H*(NO'^)^0'' (Dessaignes). This body may be obtained 
in crystals, but it is not stable. Its aqueous solution decom- 
poses between 40 and 50°, with a brisk effervescence of carbon 
dioxide, and formation of oxalic acid. When the decompo- 
sition takes place below 36°, a peculiar, crystallizable acid is 
formed, which Dessaignes has named tartronic acid. Its com- 
position corresponds to the formula CTI^O^ = C'IPO'(OH)^ 

TARTRATES. 

Tartaric acid is dibasic ; it contains two hydrogen atoms 
which are replaceable by an equivalent quantity of metal. 
Neutral tartrates and acid tartrates are known. 

^ I C*H*06 ^, I C*n^06 Jj' [ CiII^OG, or R"C^1I^0« 

Tartaric acid. Acid tartrates. Neutral tartrates. 

Neutral tartrates are known in which one atom of metal is 
replaced by a monatomic oxidized e;roup, such as (SbO)', 
(FeO)', (BoO)'. 

Potassium Tartar-emetic. Ferro-potassium tartrate. Boro-potassium 

acid tartrate. tartrate. 

Potassium Acid Tartrate, or Cream of Tartar, KHC'H*0^ 

is prepared from the crude tartar of wine-casks Ijy subjecting 
that product to several crystallizations in boiling water. It 
crystallizes in right rhombic prisms, very slightly soluble in 
water. If a concentrated solution of tartaric acid be added 
to a saturated solution of potassium chloride, a precipitate of 
potassium acid-tartrate will be formed on agitating the liquid. 

Potassium Neutral Tartrate, K-C'H'O".— This salt is pre- 
pared by neutralizing a boiling solution of cream of tartar 
with potassium carbonate. The evaporated solution deposits 
on cooling oblique rhombic prisms, very soluble in water. 

Potassium and Sodium Tartrate, ^\ } c^ii^oe + 4H2o._This 
salt, which is much used in medicine, was discovered in 1672 
by Seignette, a pharmacist of Rochelle ; hence it is often called 
Rochelle salt, or Seignette's salt. It is prepared by neutralizing 
a boiling solution of cream of tartar with sodium carbonate, and 
evaporating the solution. On cooling, the double tartrate is 
deposited in large, beautiful crystals, eight-sided right rhombic 
prisms. 



ANTIMONIO-POTASSIUM TARTRATE. 557 



ANTDIONIO-POTASSIUM TAKTRATE, OR TARTxVR- 
EMETIC. 

This salt is prepared by boiling cream of tartar with water 
and oxide of antimony, which dissolves abundantly in the 
liquid. After filtration and cooling, the salt is deposited in 
crystals which are purified by a second crystallization. 

Tartar-emetic crystallizes in rhombic octahedra, and the crys- 
tals, which contain one molecule of water of crystallization for 
two molecules of salt, effloresce in dry air. 

Its taste is astringent and nauseating. It dissolves in 14,5 
parts of cold water and in about two parts of boiling water. 
It is insoluble in alcohol. 

When heated to 200° it loses the elements of water and is 
converted into a double tartrate of antimony and potassium, in 
which the trivalent antimony replaces 3 atoms of hydrogen in 
the tartaric acid. 

C*H\SbO)'KO« = C^H^SV'HKO*^ + H^O 

When heated to redness in a small, covered crucible, tartar- 
emetic leaves an alloy of potassium and antimony, disseminated 
in a mass of charcoal. When this mass is exposed to moist 
air, it suddenly takes fire and explodes, projecting brilliant 
sparks. 

The following are the characteristics of a solution of tartar- 
emetic : 

Hydrogen sulphide forms an orange precipitate of antimony 
sulphide. 

A few drops of hydrochloric acid cause the appearance of 
a white precipitate of antimony oxychloride, which disappears 
in an excess of acid. 

Potassium hydrate produces a white precipitate of antimony 
oxide, which redissolves in an excess of alkali. 

A plate of tin immersed in a solution of emetic precipitates 
metallic antimony as a black deposit. 

Tartar-emetic is a much employed medicine. In large doses, 
or smaller ones frequently repeated, it is an energetic poison. 

Ferro-Potassium Tartrate. — This salt is prepared by dis- 
solving ferric hydrate in cream of tartar, and evaporating the 

47^ 



558 ELEMENTS OF MODERN CHEMISTRY. 

solution. It forms brown, amorphous scales, very soluble in 
water. It is used in medicine. 

Boro-potassium Tartrate is formed when boric acid is dis- 
solved in a boiling solution of cream of tartar. It is an amor- 
phous salt, very soluble in water. 

PARATARTARIC ACID. 

(J8H12012 4- 2H20 

This acid, which is isomeric with tartaric acid, exists in cer- 
tain tartars. It was discovered in 1822 by Kestner, and has 
been studied by Berzelius and by Pasteur. 

It crystallizes in transparent, dissymetric prisms, whicli efflo- 
resce in the air, losing their water of crystallization. It dis- 
solves in 5.7 parts of water at 15°. Its solution does not 
change the plane of polarized light, but Pasteur has succeeded 
in separating it into two other acids, both of which are optically 
active. One of them turns the plane of polarization to the 
right, and is ordinary tartaric acid; the other deflects it to the 
left, and is levo-tartaric acid. These two acids, which are iso- 
meric with each other, reproduce paratartaric acid when they 
are mixed in equivalent proportions. It is somewhat remark- 
able that the mixture of their solutions is attended by a 
development of heat (Pasteur). 

The solution of paratartaric acid precipitates solutions of 
sulphate, nitrate, and chloride of calcium, a character which 
tartaric acid does not possess. 

Independently of dextro-tartaric acid, levo-tartaric acid, and 
paratartaric acid, there is a fourth isomeride, which is uinctive 
tartaric acid. It exerts no action on polarized light, and cannot 
be separated into two active acids (Pasteur). 

Jungfleisch has shown that these various modifications of tar- 
taric acid may be produced at will by the action of a tempera- 
ture of about 170° on a solution of ordinary tartaric acid. 

CITRIC ACID. 

CeRsOf 

This acid, discovered by Scheele in 1784, is largely diffused 
throughout the vegetable kingdom. It exists in lemons, oranges, 
limes, currants, raspberries, cherries, etc. 

It may be advantageously prepared from lemon-juice, which 



URIC ACID. 559 

is allowed to stand until it begins to ferment, and is then filtered, 
and saturated with chalk while l)oiling. The precipitate of 
calcium citrate is washed with boiling water, and decomposed 
by a slight excess of dilute sulphuric acid. The liquid sepa- 
rated from the calcium sulphate yields crystals of citric acid 
after concentration. 

This acid forms large, colorless crystals, derived from a right 
rhombic prism. It dissolves in three-fourths its weight of 
cold and half its weight of boiling water. 

When heated, it melts. At 175° it disengages water, and 
is transformed into a pyrogenous acid, which is identical with 
the aconitic acid that may be extracted from aconite. 

c«H«o^ = c'li'O' — ir^o 

Aconitic acid. 

If the heat be increased, carbon dioxide is disengaged, inde- 
pendently of some accessory products, and oily streaks appear 
in the neck of the retort, and solidify to a crystalline mass. 
This product is itaconic acid. A portion of the distilled 
product remains liquid ; it is the anhydride of a third pyroge- 
nous acid, isomeric with the preceding, and called citraconic 
acid. 

Q6JJ606 ^ Q^WO' -f CO^ 
Aconitic acid. Itaconic and 

Citraconic acids. 

Citraconic acid. Citraconic anhydride. 

Fused potassium hydrate converts citric acid into oxalic and 
acetic acids. 

The solution of citric acid has an acid reaction and a very 
sour taste. It does not precipitate lime-water in the cold, but 
the solution becomes clouded after boiling. 

Citric acid is tribasic. 

Magnesium citrate, which is soluble, is employed in medi- 
cine ; it is a purgative, having a sweetish taste. Ferric citrate 
also is used in medicine. 

UEIC ACID. 

C5H*N403 

This body is related to the complex organic acids which 
have just been studied. Among the numerous products de- 



560 ELEMENTS OF MODERN CHEMISTRY. 

OTT 

rived from its oxidation, we may mention oxalic acid, C'0'<Cr\rT, 

OH . . 

and an acid, C'^0'-<()ijj wliieli has been called mesoxalic. 

Uric acid itself seems to be related, according to Baeyer, to 
tartronic acid, — one of the products of the transformation of 
tartaric acid (page 556). 

Uric acid was discovered by Scheele, and its numerous meta- 
morphoses were the subject of a classic research by Liebig and 
Wohler, and have been more recently studied by Baeyer and 
other chemists. 

Preparation. — Uric acid may be extracted from the excre- 
ments of serpents, from guano, and from certain urinary cal- 
culi, which are almost entirely composed of it. These sub- 
stances are reduced to a fine powder, boiled with potassium 
carbonate and lime, and the solution filtered. The colored 
solution of potassium urate is mixed with a solution of ammo- 
nium chloride, which produces a white precipitate of ammonium 
urate. This salt is well washed, and treated with hydrochloric 
acid, which sets free uric acid. 

Uric acid may be obtained from guano by boiling that sub- 
stance with an aqueous solution of borax (borax 1, water 120). 
The boiling solution is filtered, and after cooling is precipitated 
by hydrochloric acid. 

Properties. — Pure uric acid is a light, white powder, which 
has a crystalline aspect under the microscope. When slowly 
separated from dilute solutions, it sometimes forms larger crys- 
tals, containing 2 molecules of water of crystallization. It is 
often deposited from urine in small rhomboidal tables of a 
brownish-yellow color. 

Uric acid is insoluble in alcohol and in ether. It requires 
15,000 parts of cold water, or 1800 parts of boiling water, 
for its solution. It dissolves in solutions of the alkalies, form- 
ing neutral urates containing two atoms of the alkaline metal. 
It is therefore a dibasic acid. When carbonic acid gas is 
passed into a solution of a neutral urate, an acid urate, which 
is almost insoluble, is precipitated. 

Hydrochloric acid forms a thick, white, gelatinous precip- 
itate of uric acid when added to the solution of a urate. 

When uric acid is heated to 160 or 170° with an excess of 
hydriodic acid, it absorbs water, and is decomposed into glyco- 
col, carbonic acid gas, and ammonia (Strecker). 



METAMORPHOSES OP URIC ACID. 561 



C5jj4^4Q3 _|_ 5IPQ ^ c-iPNO^ + 3C0- + SNIP 

Uric acid, Glycocol. 

If a small quantity of uric acid be gently heated with nitric 
acid in a porcelain capsule, it is dissolved with a disengagement 
of red vapors, and the solution, evaporated at a gentle lieat, 
leaves a residue which assumes a purple color on the addition 
of a drop of ammonia. 

This test is characteristic of uric acid, and permits the de- 
tection of the least traces of that substance. The purple body 
formed is called murexide. 



METAMORPHOSES OF URIC ACID. 

Alloxan, C^H'N'O^ — This body is one of the products of 
the oxidation of uric acid by nitric acid ; urea is formed at the 
same time. 

C^H^N^O' + H^O + O =: C^H^N^O* + CH^N^O 

Uric acid. . Alloxan. Urea. 

It may be prepared by introducing uric acid, in successive 
small quantities, into nitric acid of a density of 1.41-1.42, as 
long as it dissolves producing red vapors. The alloxan finally 
separates in a mass of delicate needles ; in about twenty-four 
hours they are drained and dissolved in water at 60 or 65°. 
On cooling, the alloxan separates in voluminous crystals con- 
taining 4 molecules of w^ater of crystallization. They efflo- 
resce in dry air. 

When crystallized from a hot solution, alloxan forms rhombic 
octahedra, containing but a single molecule of water. 

It is very soluble in water, and the solution is acid. By the 
action of alkalies, baryta-water for example, alloxan is con- 
verted into aUoxonic acid., which is formed by the direct com- 
bination of the elements of one molecule of water with alloxan. 

C^H^N^O* + H^O = C^H^N^O^ 

Alloxan. Alloxanic acid. 

The alloxanates are decomposed by boiling into mesoxalic 
acid and urea. 

C^H^N^O^ + H^O = C^O^H^ + CH^N^O 

Alloxanic acid. Mesoxalic acid. Urea. 

Mesoxalic acid, C^0^(0H)2 = CO.OH-CO-CO.OH, is a 
dibasic acid. According to Baeyer, its diatomic radical, mes- 



562 ELEMENTS OF MODERN CHEMISTRY. 

oxalyl, exists in alloxan itself, which is mesoxalylurea, that 
is, urea in which two atoms of hydrogen are replaced by the 
diatomic radical (C'O^)". 

(CO)") (CO)") 

H2lN2 (Cao:i)"yN2 

m J 112 j 

Urea. Mesoxalylurea 

(alloxan). 

Parabanic Acid, C^H^N^Ol— This body is formed by the 
action of an excess of nitric acid on alloxan, which thus gives 
up the elements of carbon dioxide. 

Alloxan. Parabanic acid. 

Parabanic acid forms thin, transparent prisms, which are 
very soluble in water. By boiling with acids, it is transformed 
into oxalic acid and urea. Baeyer regards it as oxalylurea. 

(CO)") 

(C202)" IN2 
H2J 

When parabanic acid is heated with ammonia, ammonium 
oxalurate is formed, and separates in fine needles. In this 
case the parabanic acid is converted into oxaluric acid by 
directly combining with the elements of water. 

C3JJ2^2Q3 _^ JJ20 ^ C^H^N^O* 

Parabanic acid. Oxaluric acid. 

It is seen that oxaluric acid is related to parabanic acid, as 
alloxanic acid is to alloxan. 

AUoxantin, C®H*N*0^ — This body is produced by the re- 
duction of alloxan. When a current of hydrogen sulphide is 
passed through a cold solution of alloxan, sulphur separates, 
and a crystalline precipitate of alloxantin soon forms. 

2eHW0* + H'^S = C«H*N*0' + H^O + S 

Alloxan. Alloxantin. 

Alloxantin is also formed directly, at the same time as 
alloxan, by the action of weak nitric acid on uric acid. It 
crystallizes in small, colorless prisms containing 3 molecules 
of water of crystallization. It is but slightly soluble in cold 
water. Nitric acid converts it into alloxan, and reducing agents 
transform it into dialuric acid. 

Dialuric Acid, C^H*N'0\ is the product of the prolonged 



METAMORPHOSES OF URIC ACID, 563 

action of hydrogen sulphide on a hot sohition of alloxan or 
alloxantin. 

C*ir-N'0* -f WS = C^H^N'^0* + S 

Alloxan. Dialuric acid. 

It is also formed by the action of sodium amalgam on the 
same solutions. 

It crystallizes in long needles, quite soluble in water ; these 
crystals assume a red color in the air, and are gradually trans- 
formed into alloxantin. 

When a solution of alloxan is added to a solution of dialuric 
acid, alloxantin is formed. 

Dialuric acid. Alloxan. Alloxantin. 

Baeyer regards dialuric acid as tartronyl-urea, that is, urea 
in which two atoms of hydrogen are replaced by the diatomic 
radical of tartronic acid, C^H'-^O^OH J^ = CO.OH-CHCOH)- 
CO.OH. 

(CO)") (CO)") 

H2 j 112 j 

Urea. Dialuric auid 

(tartronyl-urea). 

Purpuric Acid and Murexide. — Scheele had already ob- 
served murexide, which Prout studied and described as pur- 
piirate of ammonia. It is, indeed, the ammonium salt of a 
nitrogenized acid, C^H^N^O'^, for which it is convenient to pre- 
serve the name purpuric acid (Beilstein). 

Murexide is formed by the action of ammonia on dry allox- 
antin heated to 100°, or again, when ammonia or ammonium 
carbonate is added to a hot solution of alloxantin or alloxan. 

C^H*N^O^ + 2NH3 = C^H*(NIP)N^O« + H^O 

Alloxantin. Murexide (ammonium purpurate). 

Murexide crystallizes in quadrangular prisms, or in tables 
which are green by reflected and red by transmitted light. 
These crystals, which contain one molecule of water, present 
the magnificent metallic reflections shown by the wings of can- 
tharides. They dissolve in water with a rich purple color. 

AUantoin, C^H'^N^Ol— This body was discovered in 1800, 
by Yauquelin and Buniva, in the allantoic liquid of the cow, 
that is, the urine of the foetal calf. It occurs also in the urine 
of young calves. In 1836, Liebig and Wohler obtained it by 
oxidizing uric acid with lead dioxide. Gorup-Bcsanez has 
observed its formation in the action of ozone upon uric acid. 



564 ELEMENTS OF MODERN CHEMISTRY. 

Grimaiix has recently made the synthesis of alhintoin by 
heating one part of glyoxylic acid with two parts of urea, for 
eight or ten hours. 

Q2H.Q3 _|_ 2(CH*N^0) = C*W'^'0' + 2H^0 

Glyoxylic acid. Urea. Allantoiu. 

From this remarkable synthesis, it appears that allantoin is 
derived from two molecules of urea ; it is the diureide of gly- 
oxylic acid. 

Allantoin may be prepared by boiling uric acid with water, 
and adding lead dioxide, in small quantities, as long as that 
oxide continues to be converted into a white powder, which is 
lead carbonate. The filtered liquid, freed from lead by hydro- 
gen sulphide, yields crystals of allantoin on evaporation. 

Uric acid. Allantoin. 

Allantoin crystallizes in brilliant, colorless prisms. It dis- 
solves in 30 parts of boiling water and in 160 parts of cold 
water ; it is also soluble in alcohol, but is insoluble in ether. 
It forms crystallizable compounds with certain metallic oxides. 



We cannot further continue the study of the numerous de- 
rivatives of uric acid. This study has already thrown great 
light upon the constitution of the acid, which Baeyer regards 
as derived from tartronic diamide, that is, the diamide corre- 
sponding to tartronic acid. 

C3H203 1 OH C3H203 1 ^'g' C3H203 1 NH.CN 

Tartronic acid. Tartronic diamide. Tartronic dicyajianiide 

(uric acid). 

Grimaux has recently made the synthesis of alloxan ; all 
of the members of the uric series can thus be obtained synthet- 
ically, excepting uric acid itself. 



ALCOHOLS OF HIGHER ATOMICITY. 

One tetratomic alcohol is known with certaint3^ It is ery- 
thrite, of which de Luynes recognized the true nature. 

Glucose, which Berthelot regarded as a hexatomic alcohol, 
seems to fill a mixed function: it is at the same time an alde- 
h3'de and a pentatomic alcohol. 



ERYTIIRITE. 5G5 

The best characterized hexatomic alcohol is mannite, a sweet, 
crystallizable substance, which is extracted from inaiina. Glu- 
cose is related to manna, from which it differs only by two 
atoms of hydrogen. The constitution of mannite may be ex- 
pressed by the following formula : 

It results from the experiments of Linnemann that various 
saccharine matters, possessing the composition C'lP-O'', fix li'* 
directly under the influence of sodium amalgam and water, and 
are converted into mannite. The latter body is characterized 
as a hexatomic alcohol by the property which it possesses of 
forming neutral compounds with G molecules of a monobasic 
acid, such as acetic acid. In other words, this body contains 
G hydroxyl groups, or six atoms of hydrogen capable of being 
replaced by G monobasic acid radicals. 

ERYTHRITE. 

C4H10O1 = C^H6(0H)* 

This beautiful body was discovered in 1849 by Stenhouse, 
who found it among the decomposition products of erythric 
acid or erythrin, a substance contained in certain lichens. In 
1852, Lamy obtained from an algae, the Protococcus vulgaris^ 
a substance which he first named phycite, but which he after- 
wards recognized to be identical with erythrite. 

Preparation. — Do Luynes first extracts erythrin from a 
lichen, the Rocclla Montagaei^ and decomposes it, while still 
moist, by slaked lime in closed vessels at a temperature of 
150°. Under these conditions, erythrin is decomposed into 
carbonic acid which is at once taken up by the lime, orcin, and 
erythrite, which are separated by crystallization, the orcin being 
deposited first. The erythrite is purified by washing it with 
ether, which removes a trace of orcin. 

Properties. — Erythrite crystallizes in right square prisms. 
The crystals are hard, have a feeble, sweet taste, and are very 
soluble in water, soluble in boiling absolute alcohol, and insol- 
uble in ether. They melt at 130°. Erythrite reacts with the 
acids, forming neutral bodies analogous to the ethers (Berthelot). 

When heated with a concentrated solution of hydriodic acid, 
it is converted into secondary butyl iodide (de Luynes). 
C*H^W + 7HI = C*H^I 4- 4H^0 + SP 

Erythrite. Secondary butyl iodide. 

48 



566 ELEMENTS OP MODERN CHEMISTRY. 

MANNITE. 

C6Hi*06 = C6H8(OH)6 

This body, discovered by Prout in 1806, exists in a great 
number of vegetables. It is the most abundant constituent of 
manna, a substance which flows from several species of ash, 
either naturally or from incisions. It is prepared by dis- 
solving manna in distilled water, in which the white of an egg 
has previously been beaten up. The solution is boiled several 
minutes and then filtered through a woollen cloth and allowed 
to cool. The liquid then solidifies to a mass of crystals which 
are purified by recrystallization after treatment with animal 
charcoal. 

Mannite forms large, right rhombic prisms. Its taste is 
sweet, and it is soluble in water and alcohol. 

When heated with a concentrated solution of hydriodic acid, 
it is reduced to a secondary hexyl iodide. 

Maunite. jS-secondary hexyl iodide. 

Berthelot has described a secondary hexa-stearic mannite^ 
containing C^H^CC^^H^^ O'^f. 

But, by the action of many acids upon mannite, compounds 
are obtained which are not ethers of mannite, strictly speak- 
ing, but of an anhydride of that body, to which Berthelot has 
give the name mannitan. 

Q6JJ14Q6 _ H2Q ^ C«H^^O^ 

Manuite. Manuitan. 



Mannitan is isomeric with two sweet substances, qiiercite, or 
the sugar of the glands, which was discovered in the glands by 
Braconnot, andp/^^/Vc, which has been extracted by Berthelot 
from the resin of the California pine. 

Dulcite^ C^H^*0*^, which has been obtained from Madagascar 
manna, exists in certain plants, such as the Mdamj^ynmi 
ncmorosum^ the Scropludaria nodosa^ the Rhinantlius cn'sfa- 
galU^ and the Euonymns curopseus. It forms large, oblique 
rhombic prisms, and is less soluble in water than mannite ; it 
is but slightly soluble in alcohol. It melts at 188.5°. It dis- 
solves in the hydracids without producing heat. Like its 



SUGARS AND STARCHES. 5G7 

isomeride, manna, it is reduced by hydriodic acid to a second- 
ary liexyl iodide (G. Bouchardat). 

Sorhife, C'lr^O", recently obtained by J. Boussingault from 
the fermented juice of the mountain-ash, is another isomeride 
of mannitc. 



SUGARS AND STARCHES. 

Among the more widely distributed products of the vege- 
table kingdom must be included the various kinds of sugar, 
starch, the gums, and the matter of young vegetable cells, or 
cellulose. 

These compounds contain carbon, hydrogen, and oxygen in 
such proportions that the oxygen is present in exactly sufficient 
quantity to form water with the hydrogen. Their composition 
is then expressed by the general formula C^CH'-^O)". If all of 
the oxygen and hydrogen were removed in the form of water, 
only carbon would remain. Hence the name hydrates of car- 
bon, often applied to this class of bodies. 

Some of them contain 6, and the others 12 atoms of carbon, 
and they can be arranged in three different classes, of which 
the types are glucose, saccharose, and starch. 

Glucose, or grape-sugar, contains CH'-O*'. 

Saccharose, or cane-sugar, contains C^"^H"0^^ 

Among the important sugars of this type, we may mention 
lactose, or milk-sugar. 

Starch, or amylaceous matter, has a composition expressed 
by the formula C^H^^O^. Its most important isomerides are 
dextrin, inulin, the gums, and cellulose. 

xill of these bodies have the power of rotating the plane of 
polarized light, either to the right or to the left. 

They react with several molecules of an acid, forming neu- 
tral compounds, a property which characterizes them as poly- 
atomic alcohols (Berthelot). 



GLUCOSE. 

C6H1206 

This important body, which forms the solid and crystalliza- 
ble part of honey, exists in a great number of dried fruits, on 
the surface of which it forms a well-known white efflorescence. 



568 ELEMENTS OF MODERN CHEMISTRY. 

It is also found in the urine in the disease known as diabetes. 

It may be made artificially by the action of dilute sulphuric 
acid on starch (Kirchhoff), or on cellulose (Braconnot). 

Preparation. — Glucose is prepared in the arts by the fol- 
lowing process : 

0000 litres of water and 42 kilogrammes of sulphuric acid 
are introduced into a large wooden trough, and the liquid is 
heated by jets of superheated steam. When it is in full ebul- 
lition, 2000 kilogrammes of starch suspended in 2000 litres 
of warm water are allowed to run in gradually, and in thirty 
or forty minutes the saccharification is complete. The sul- 
phuric acid is then saturated with pulverized chalk, the insol- 
uble calcium sulphate is separated, and the liquid concentrated 
in boilers heated by steam until it marks 40 or 41° Baume. 
It is then allowed to crystallize, and solidifies to an opaque, 
yellowish, crystalline mass, which is glucose. 

The sulphuric acid has recently been rejjlaced by hydrochlo- 
ric acid, which produces a whiter product. The small quantity 
of calcium chloride formed does not prevent the crystallization 
of the glucose. 

Properties. — This body crystallizes in small, white, rounded 
masses, agglomerated like cauliflowers. The crystals contain 
one molecule of water of crystallization (C^H^'O*'' -[- H^O). 
They remain unchanged in the air. They melt when heated 
on a water-bath, and lose their water at 100^. Anhydrous 
glucose melts at 144°. 

Glucose dissolves in a little more than its own weight of 
water at 17°. It is three times less soluble than cane-sugar, 
and in solutions of equal concentration it is three times less 
sweet. It is much less soluble in alcohol than in water. 

The solution of glucose rotates the plane of polarization to 
the right ([a] D = 56.4°). 

When glucose is heated to 1T0°, it loses the elements of 
water and is converted into a colorless mass, not very sweet, 
which has received the name glucosan. 

Glucose. Glucosan. 

Glucose forms true compounds with the bases. There is a 
glucosatc of calcium. CH'Ta'D" + WO. It is precipitated 
when alcohol is added to a solution of calcium hydrate in glu- 
cose. 



GLUCOSE. 5G9 

These compounds are not stable. 

If potassium hydrate bo added to a solution of glucose and 
the litjuid be heated, it first becomes yellow, and then rapidly 
assumes a deep-brown color. The same color is produced when 
glucose is heated with calcium or barium hydrate. 

According to Peligot, there are formed under these circum- 
stances two acids, which he named glucic and melassic acids. 
Ordinary or cane-sugar does not produce this reaction, and can 
thus be distinguished from glucose. 

Glucose reduces various metallic solutions. If a solution of 
cupric sulphate be poured into a solution of glucose, and potas- 
sium hydrate be added, no precipitate is formed, but the liquid 
acquires a dark-blue color. On heating it, a yellowish precip- 
itate of cuprous hydrate is formed. 

This reaction, which was discovered by Trocmmer, is very 
sensitive, and can be used for the detection of the smallest 
quantities of glucose. In making the test, a cupro-alkaline 
solution is employed, made by dissolving cupric tartrate in 
potassium hydrate (Barreswill's solution), or by adding sodium 
and potassium tartrate and caustic soda to a solution of cupric 
sulphate (Fehling's solution). 

AVhen a solution of glucose is heated with bismuth nitrate 
and an excess of potassium hydrate, a black precipitate of 
reduced metallic bismuth is formed. 

When a solution of common salt is added to a solution of 
glucose and the liquid is allowed to evaporate spontaneously, 
crystals are deposited which constitute a definite compound 
of the two bodies. They contain 2(NaCl + 2C'tr^0*') + 
3H^0. 

Glucose forms combinations with the acids, like mannite, and 
these combinations represent glucose in which a certain num- 
ber of hydrogen atoms are replaced by acid radicals. Ber- 
thelot had regarded glucose as a hexatomic alcohol, containing 
6 hydroxyl groups, but Colley has shown that it is a penta- 
tomic alcohol. He has described a compound produced by the 
action of acetyl chloride on glucose, and which he names aceto- 
cldorliijdrose. It contains 

C^H^O I (Q2JJ3Q2)4 

On account of the reducing properties of glucose, it may 
be considered that the oxygen atom of the group C^H^O forms 

48- 



570 ELEMENTS OP MODERN CHEMISTRY. 

part of an aldehyde group CHO. Hence glucose is at the 
same time an aldehyde and a pentatoniic alcohol, and its 
constitution would be represented by the formula CH-.OH- 
CH.OPI-CH.OH-CH.OH-CH.OH-CHO. 

The following fact supports this view. When chlorine gas 
is passed into a solution of glucose, the latter is converted into 
an acid, gluconic acid, CH^'O^, which only differs from glucose 
by containing one more atom of ox^^gen. This acid corre- 
sponds to gluconic aldehyde, and the following formulae indi- 
cate the relations existing between the bodies just mentioned : 



CH2.0H 


CH2.C1 


cn2.0H 


(CH.OH)* 


(CH.ocmso)* 


(CH.0H)4 


CHO 

Glucose. 


CHO 

Acetoclilorhydrose. 


CO.OH 
Gluconic acid. 



LEVULOSE, OR UNCRYSTALLIZABLE FRUIT- 
SUGAR. 

C6H1206 

Independently of the glucose which effloresces on their 
surface after desiccation, many fruits contain another sugar, 
incapable of crystallization, and which strongly deviates thQ 
plane of polarization to the left. It is levulose. 

Levulose exists in inverted sugar (page 574). Many sweet 
fruits contain inverted sugar ; among them are grapes, cherries, 
figs, gooseberries, etc. 

It may be extracted from inverted sugar (a mixture of equal 
proportions of glucose and levulose). Dubrunfaut recommends 
the following process : 10 grammes of inverted sugar, G grammes 
of slaked lime, and 100 grammes of water are intimately mixed. 
The mass, which is at first liquid, becomes pasty on agitation, 
and then contains a solution of calcium glucosate and solid cal- 
cium levulosate. It is strongly pressed in a cloth and the 
compound of levulose and lime is decomposed by oxalic acid. 
The levulose remains in solution, and after evaporation forms 
an uncrystallizable syrup which is much sweeter than a solu- 
tion of glucose. 

Levulose is directly fermentable. When heated to 1.70°, it 
loses the elements of water and is converted into Icvulosan. 

C«H'^0« = C^H'^O^ + H^O 

Levulosan. 



SACCHAROSE. 5*7 1 

Other sugars are known which may be chissed with glucose. 
Such are the following : 

1. Sorbin, C'lP'O", a substance which crystallizes in large, 
transparent rhombohedra ; has been obtained from the berries 
of the mountain-asli by Pelouze. 

2. Inosite, C^^H^-C^ + H'O, a sugary matter extracted by 
Scherer in 1850 from the muscles, and which has since been 
found in the lungs, kidneys, spleen, and liver (Cloetta). In- 
osite is identical with a substance that Vohl extracted from 
green beans, and to which he gave the name j^haseomannife. 

Inosite forms large, rhombic tables, or transparent, colorless 
prisms, having a sweet taste. The crystals effloresce in the air. . 
They are soluble in water, but insoluble in absolute alcohol and 
in ether. The aqueous solution is optically inactive ; it is not 
converted into glucose by the action of dilute acids ; it does 
not reduce cupro-potassic solutions, nor will it ferment under 
the influence of yeast. 

SACCHAROSE, OR CANE-SUGAR. 

C12H22011 

Extraction. — Ordinary sugar, which is universally diflfused in 
the vegetable kingdom, is extracted principally from sugar-cane, 
sugar-maple, and beet-root. Fresh sugar-cane contains about 
eighteen per cent, of sugar : beet-root contains only about ten 
per cent. (Peligot). 

Certain sweet fruits contain cane-sugar, independently of 
inverted sugar. According to Buignet, such are apricots, 
peaches, pine-apples, lemons, plums, and raspberries. 

We can only briefly indicate the processes which are em- 
ployed for the extraction of sugar from beet-root. 

The roots are washed, and reduced to pulp in a machine 
provided with a cylinder armed with teeth and having a rapid 
rotary motion. This pulp is then strongly pressed in woollen 
sacks by means of a hydraulic press, and the juice is imme- 
diately transferred to large boilers having double bottoms and 
heated by steam, and milk of lime is added. 

This operation, which is called defecation, is intended not 
only to separate certain substances which form insoluble com- 
pounds with the lime, but to prevent the juice from becoming 
altered by reason of its acidity. As the sugar itself dissolves 
a large quantity of lime, the latter must be got rid of. A cur- 



572 ELEMENTS OF MODERN CHEMISTRY. 

rent of carbon dioxide is consequently passed into the solution, 
and decomposes the saccharate of calcium. Another process 
of dcchaidage^ recently devised, depends on the employment 
of ammonium phosphate. Insoluble calcium phosphate is 
formed, and the ammonia is disengaged on account of the high 
temperature at which the operation is conducted. By this 
process the neutralization is more perfect. 

The liquid is then heated to about 95°, and filtered through 
a layer of animal charcoal in grains ; it is then concentrated in 
evaporating-pans heated by steam. When the syrup marks 
25° Baume, it is again filtered through animal charcoal, and 
the concentration is finished in pans heated by steam, and in 
which a vacuum is maintained during the evaporation. The 
cooking of the syrup is thus carried on at a temperature not 
above 75 or 80°, and these conditions assure a fine quality of 
product and a good yield by preventing as much as possible 
the transformation of the sugar into uncrystallizable sugar. 

When the syrup marks 42 or 43°, it is run into cooling- 
pans, where it is continually stirred until the sugar is depos- 
ited in small crystals. These are distributed in moulds, which 
consist of terra-cotta cones having a hole in the summit, which 
for the time is closed. These cones are placed in an oven 
heated to 25°, where the crystallization takes place ; when the 
syrup has solidified, the holes in the cones are opened and the 
thick and colored mother-liquor is allowed to drain out ; it con- 
stitutes molasses. The loaves of sugar, drained and dried, are 
delivered to commerce as crude or brown sugar. 

For some years an apparatus has been used for draining 
and bleaching of crude sugars, which consists of a cylindrical 
cage having perforated metallic walls. It is put into rapid 
motion on its axis, and the molasses is expelled through the 
perforated walls by centrifugal force. The apparatus is called 
the centrifugal drier. 

Refining of Crude Sugar. — The crude sugar is crushed, 
sifted, and dissolved in about 30 per cent, its weight of water, 
the operation being conducted in a boiler heated by steam. 5 
per cent, of animal charcoal is then thrown into the hot solu- 
tion, and, after stirring, h per cent, of beef's blood is added. 
The latter coagulates in the liquid and envelops all of the sus- 
pended particles, uniting them in a scum which is easily re- 
moved. When the li(|uid becomes clear, it is drawn oft' and 
filtered. It is then passed through grained animal charcoal, 



SACCHAROSE. 573 

which completely decolorizes it. It is concentrated in vacuum- 
pans, from which it is drawn into a large copper vessel having 
a double bottom. It is continually stirred until crystallization 
commences, after which it is run into moulds, which are then 
placed in rooms heated to 20°. After the crystallization is 
completed, the syrup remaining liquid is allowed to drain out. 

At the termination of the draining, a creamy mixture of 
white clay and water is poured on the surface of the sugar in 
each mould, and the water of this broth slowly penetrates the 
mass of sugar, liquefies the syrup which remains between the 
crystals, and carries it to the lower part of the mass. The clay, 
having lost its water, contracts, dries up, and remains upon the 
decolorized sugar as a dry cake. It is removed, and a syrup 
of white sugar is run into the whitened and porous loaf and 
fills up all of the spaces when it solidifies in the oven. 

This operation, the object of which is the decolorizing of 
the sugar-loaves, is called claying. The clay broth may be 
replaced by syrup of white sugar, an operation which is called 
decoloring. 

The sugar solidified in the moulds is a compact, crystalline, 
white mass, composed of little grains. It may be obtained in 
voluminous crystals by concentrating the syrup until it marks 
37° Baume, and then exposing it for some days to a tempera- 
ture of 30° in copper vessels, across which threads are stretched. 
The sugar is deposited on the threads in large crystals known 
as rock-candy. 

Properties of Sugar. — Sugar crystallizes in large, oblic|ue 
rhombic prisms, having hemihedral facettes. The crystals are 
hard, anhydrous, and unalterable in the air. It dissolves in 
one-third its weight of cold water ; the solution is thick, and is 
known as simple syrup. Sugar is insoluble in ether and in 
cold absolute alcohol. Boiling absolute alcohol dissolves a little 
more than one per cent. ; ordinary alcohol will take up more. 

The aqueous solution of sugar deviates the plane of polari- 
zation to the right, ([a]D = -f 67°). 

At 160°, sugar melts to a thick, transparent liquid, which 
solidifies to an amorphous, vitreous mass on cooling. 

When maintained for a long time at a temperature of 160 
or 161°, it breaks up into glucose and levulosan (Gelis). 
(;il2JJ22Qll ^ C«H^^O« + C^H^»0^ 
Saccliarose. Glucose. Levulosan, 

Between 190 and 200° it loses the elements of water and is 



574 ELEMENTS OF MODERN CHEMISTRY. 

converted into a bitter, brown, amorphous mass, which is desig- 
nated as caramel. 

Inverted Sugar. — By the action of dikite acids, sugar is 
converted, slowly in the cold and rapidly on boiling, into a 
mixture, in equal proportions, of two isomeric sugars which 
have opposite rotatory powers : they are glucose and levulose. 
The mixture is called inverted sugar. 

Q12JJ22QU _!_ JJ2Q ^ C'H^^O^ + C^H^^O^ \ 

Saccharose. Glucose. Levulose. 

The same transformation is effected by the soluble matter 
of yeast (Berthelot), and also, according to Buignet, by the 
action of the peculiar ferments which exist in most fruits. 

Sugar only ferments after having first undergone this trans- 
formation into inverted sugar by the action of the ferment. 

Nitric acid converts sugar into saccharic acid., CH^^O**, and 
oxalic acid. 

Concentrated sulphuric acid carbonizes it. 

Saccharose resists the action of alkalies better than glucose. 
It forms with them and with the bases in general, definite com- 
binations known as saccharates. 

If a mixture of sugar and slaked lime be triturated with 
water and the whole be thrown upon a filter, the liquid which 
passes through will be colorless and strongly alkaline. When 
it is heated to ebullition, it changes into a solid mass which 
again becomes liquid on cooling. It is a solution of saccharate 
of calcium. 

An analogous experiment may be made with a concentrated 
boiling solution of barium hydrate. 

When sugar is heated to 150 or 160° with barium hydrate, 
it yields lactic acid. When fused with potassium hydrate, it 
disengages hydrogen, and carbonate, oxalate, formate, acetate, 
and propionate of potassium are formed. 

Sugar forms a combination with sodium chloride, consisting 
of deliquescent crystals which contain C^'^'H^O'^NaCl. 

LACTOSE, OB MILK-SUGAR. 

This sugar exists in solution in the milk of mammals, and is 
extracted from the whey which remains after the manufacture 
of cheese. It is only necessary to evaporate this liquid to 
crystallization. 



3IALT0SE. 575 

Milk-sugar occurs in commerce in cylindrical masses, formed 
of an agglomeration of crystals around a little stick which 
serves as a nucleus. The crystals are colorless, hard, and creak 
when crushed by the teeth. They are right rhombic prisms, 
terminated by octahedral points. They contain one molecule 
of water of crystallization w^hicli they lose at about 140°. 
They dissolve in G parts of cold, and in 2 parts of boiling 
water. The solution turns the plane of polarization to the 
right. 

When heated with nitric acid, lactose yields certain acids, 
among which is one which is but slightly soluble in water, and 
which is called mucic acid. It contains C'^H^'^O^, and is iso- 
meric with saccharic acid, which is also produced by the oxi- 
dation of lactose by nitric acid. Liebig found tartaric acid 
among the products of this oxidation, and a small quantity of 
paratartaric acid has also been observed to be formed (Carlet). 
Lastly, oxalic acid is also produced. 

When boiled with dilute sulphuric acid, milk-sugar is con- 
verted into glucose and another sugar isomeric with glucose, 
and to which the name galactose has been given. Galactose 
will undergo the alcoholic fermentation under the influence of 
yeast. It is crystallizable, and occurs in microscopic crystals 
united together in tufts. 

Milk-sugar reduces cupro-alkaline solutions. 

When exposed to the air at summer heat, a solution of lac- 
tose in presence of an alkaline salt or calcium carbonate soon 
undergoes the lactic fermentation (page 577). 



MALTOSE. 

C12H22011 + H20 

This name is given to the crystallizable sugar produced by 
the action of diastase on starch. It may be prepared by digest- 
ing starch paste at 60° with a solution of diastase. The solu- 
tion is precipitated by alcohol, filtered, the alcoholic liquid 
evaporated to a syrupy consistence, more alcohol added, and 
the solution set aside to crystallize in a bell-jar over sulphuric 
acid. 

Maltose forms a crystalline mass, composed of hard, white 
needles. It loses its water of crystallization at 100°. Its solu- 
tion turns the plane of polarization to the right, [«]D = -j- 



576 ELEMENTS OF MODERN CHEMISTRY. 

149.5°. It reduces cupro-potassic solutions, and when boiled 
with dilute acids is converted into glucose. 



FERMENTATION. 

If yeast be introduced into a tolerably concentrated solution 
of glucose, and the liquid be exposed to a temperature between 
20 and 30°, bubbles of an incombustible gas will soon be dis- 
engaged, and this gas will produce a cloud in lime-water. It 
is carbon dioxide. 

After the disengagement of gas has ceased, a small quantity 
of alcohol may be obtained by distilling the liquid. 

In this experiment, the glucose disappears ; it is broken up 
into alcohol and carbon dioxide. The decomposition is effected 
by yeast, and is called fermentation. The sugar is the fer- 
mentahle substance ; the yeast is \.hQferwcnt. 

The ferment is an organized matter which develops and mul- 
tiplies at the expense of the glucose. The latter, is directly at- 
tacked by this being which lives at its expense, and undergoes a 
complete decomposition, of which carbon dioxide and alcohol 
are the principal products. The ferment plays an active part, 
which was first suspected by Cagniard-Latour and Schwann, 
and demonstrated by Pasteur. 

Alcoholic Fermentation. — The decomposition of glucose 
under the influence of yeast constitutes the alcoholic fermenta- 
tion. 

It is expressed in the following equation : 

Q6JJ1206 ^ 2C^H"0 -f 2C0^ 

Glucose. Alcohol. 

It is shown by the experiments of Pasteur, that only 94 per 
cent, of the quantity of glucose decomposed undergoes the 
change indicated by the above formula. The remaining 6 per 
cent, are employed: 1, in the formation of small (juantities of 
succinic acid and glycerin ; 2, in the development of new yeast 
cells. 

Yeast is composed of a mass of cells or ovoid corpuscles, 
having a diameter of y^h ^^ ^ millimetre, and arranged in 
clusters (Fig. 125). Their walls are an elastic membrane, 
and their contents are liquid or granular. They contain cellu- 
lose, albuminoid matter, and mineral salts. When they are 




FERMENTATION. 577 

introduced into a substance which contains the materials neces- 
sary for their development, they multiply rapidly. Pasteur has 
made decisive experiments on this point. He })lanted some 
yeast cells in a solution of suuar to which he had added a small 
quantity of an ammoniacal salt and some phosphates. The solu- 
tion of sugar fermented, and the ferment developed by budding, 
the new cells absorbing the 
ammonia and the phosphates. 
They obtained from the sugar 
the matter necessary to form 
cellulose, and from the ammo- 
nia the nitrogen required for 
the elaboration of the albumi- 
noid matters. However, these 
artificial conditions are not 
those which are best adapted 
for the propagation of the cells. 
The latter increase with ex- 
treme energy in liquids which 
contain, besides the yeast, glu- 
cose, and a small quantity of Fig. 125. 
albuminoid matter ready formed. 

Lactic Fermentation. — This fermentation, of which the 
conditions have already been indicated (page 540), is accom- 
plished by the action of a peculiar ferment of vegetable char- 
acter. It is formed of small round or elongated cells, very 
short, and isolated, or in masses. They are much smaller than 
yeast cells, and constitute the lactic yeast of Pasteur. It only 
acts upon glucose or lactose in a neutral or alkaline liquid. 
Hence the necessity of adding sodium carbonate or chalk to 
the liquid. The reaction consists of a splitting of the glucose 
molecule. 

C6JJ12Q6 ^ 2C^H«0^ 

Glucose. Lactic acid. 

Butyric Fermentation. — This consists in the transformation 
of calcium lactate into butyrate, — a transformation that is ac- 
companied by a disengagement of hydrogen. According to 
Pasteur, this fermentation is caused by infusoria, and the ani- 
malculae live and are developed in situations where they are 
deprived of free oxygen. Such is the energy of their respira- 
tory functions that free oxygen kills them (Pasteur). They 
z 49 



578 ELEMENTS OF MODERN CHEMISTRY. 

respire by decomposing oxidized bodies and assimilating the 
oxygen. 

We have already considered the acetic fermentation. We 
may add that by the action of a peculiar ferment, glucose is 
converted into mannite and a gummy matter, very soluble in 
water, and which gives a viscous consistence to the fermented 
liquid. This is called the viscous fennenfaf ion. 

Fermented Beverages. — The foregoing summary indi- 
cations regarding fermentation may be completed by some 
general notions upon the fermented beverages, particularly 
wine and beer. 

Wine. — It is universally known that wine is the product of 
the fermentation of grape-juice. This juice contains in solu- 
tion inverted sugar, a small trace of gummy matters, vegetable 
albumen, a trace of fatty matters, coloring matters, free tar- 
taric and malic acids, and various tartrates, principally potas- 
sium acid-tartrate, or cream of tartar. 

The clarified wine which results from the fermentation of 
this juice contains, independently of water, various products, 
some of which existed in the juice, and others which are the 
results of the transformation through which it has passed. 
Among the first are the mineral and vegetable salts of the juice 
(in smaller proportion, because they are partly deposited with 
the lees), the gummy matter, a small quantity of fatty and 
albuminoid substances, the coloring matters, free tartaric and 
malic acids, and the tannin derived from the grape-stems and 
from the skins and seeds. x\mong the substances which result 
from the fermentation are : 

1. Alcohol, which is the principal product. 

2. Carbonic acid gas ; it is well known that it exists abun- 
dantly in champagnes. 

3. Small quantities of aldehyde and acetic acid produced by 
oxidation of the alcohol. The acetic acid reacts upon the 
alcohol contained in the wine, forming acetic ether. 

4. Grlycerin and succinic acid, in small quantities (Pasteur). 

5. Traces of compound ethers, which contribute to the bouquet 
of the wine. Besides acetic ether, traces of a compound ether 
called Genanthic ether have been found in wine ; it appears to 
be pclargouic ether, C^IP"0'(C'H^ ). Berthelot states the exist- 
ence of but slightly volatile acid ethers (malic, tartaric) in wine. 

The following table indicates the quantities by volume of 
pure alcobol contained in 100 volumes of various wines : 



FERMENTATION. 579 

Madeira 20.48 

Port 20.22 

Roussillon 10.67 

Hermitage (white) 16.03 

Malaga 15.87 

Saint-(j!eorges 15.00 

Saiitcrne (white) 15.00 

Cyprus 15.00 

Lunel 14.27 

Graves 12.30 

Frontignan 11.76 

Champagne 11.60 

Rhine 11.11 

Strongest Bordeau.\: . 11.00 

Lightest " 7.5. to 8 

Red Bourgogne 7.66 

Red Macon 7.66 

Red Chablis 7.83 

Beer. — Beer is a fermented beverage, made from a icort of 
germinated barley, and ordinarily rendered aromatic by hops. 
Like all other cereals, barley contains a considerable proportion 
of starch. During the germination, this starch is partially con- 
verted into maltose by the action of a nitrogenized matter, 
which is formed in the sprouting grains, and which is called 
diastase. In order to saccharify the barley, it is then first 
necessary to cause it to germinate, and for this purpose it is 
moistened with water, and kept for some time at 
a temperature of 14 or 15° ; the object of this 
operation, called malting, is the development of w^ ^x r 

the diastase necessary for the saccharification /^^z^fw^J^' 
of the starchy matter. When the sprout has 
acquired about the same length as the grain 
(Fig. 12G), the germination is arrested by ex- jf/l 

posing the malt to the action of a temperature \l|, 

of about 50°. The dry malt is then reduced 
to a coarse powder, placed in a large vat, and Fig. 126. 
brewed for about three hours with water heated 
to 50 or 60°. In this operation, the diastase of the malt con- 
verts the starch into dextrin and maltose, which dissolve, to- 
gether with the other soluble principles of the grain. 

The sweet wort thus obtained is heated with hops, which 
yield to it their essential aromatic oil. It is then properly 
cooled and allowed to ferment in deep vats, into which a cer- 
tain ciuantity of yeast produced in a previous operation is in- 
troduced at the same time. The alcoholic fermentation soon 
begins and goes on with great activity during a few days. As 




580 ELEMENTS OF MODERN CHEMISTRY. 

soon as it has ceased, the liquid can be delivered for consump- 
tion. The quality of beer is better when the fermentation 
takes place at a low temperature. 

Beer contains much water, free carbonic acid gas, alcohol (2 
to 5 per cent.), variable quantities of saccharine matters, dex- 
trin, nitrogenized matters, extractive, bitter, and coloring mat- 
ters, essential oil, and various salts. 

STARCH. 

C6H10O5 

Starch is universally diJBFused throughout the vegetable king- 
dom. . It is especially abundant in the seeds of leguminous 
plants and cereals, and in the potato. 

Extraction. — To extract starch from potatoes, they are re- 
duced to pulp by means of a rasp, and the pulp is placed in a 
sieve and washed by a stream of water. The water carries 
with it the fine granules of starch, while the torn cells of the 
potato remain in the sieve. The starch gradually deposits 
from the water, and collects in the bottom of the vessel, where 
it settles, forming a cake from which the supernatant water 
may be separated by dccantation. 

Starch may be extracted from wheat by making a paste of 
flour and kneeding it in a sieve under a jet of water : the starch 
granules are carried with the water, and a soft, gray, elastic 
mass remains in the sieve, constituting the nitrogenized matter 
of the flour, or gluten. 

Another process, almost abandoned at present on account of 
its off"ensiveness, consists in allowing the coarsely-ground grain 
to putrefy. Putr eviction destroys the gluten, while the starch 
resists decomposition. 

Physical Properties. — Starch is a white powder, formed of 
granules which present an organic structure. Their size and 
shape are variable (Fig. 127), their diameter being from 2 to 185 
thousandths of a millimetre. Those of potato starch are larger 
than those of starch from grain. These granules are made up 
of concentric layers, which are more dense as they are nearer 
the surface. It is easy to make this structure apparent by 
causing the granules to undergo a })artial disintegration by the 
action of hot water. Thy swell up, burst open, and separate 
into thin layers, as shown in Fig, 128. 



STARCH. 



581 



Chemical Properties. — Starch is insoluble in water, alcohol, 
and ether. Contact with water heated to (JO or 70° causes it 
to swell up considerably, without dissolvini::. xV semi-trans- 
parent, gelatinous mass results, which is known as starch })aste. 
When starch is boiled with a large (juantity of water and the 
whole is thrown on a filter, the li(|uid which passes, is slightly 
turbid, and constitutes what is known as solution of .starch. 
It contains in suspension flakes of amylaceous matter small 
enough to pass through the filter. It also contains a small 
quantity of soluble starch (see farther on). 

If a few drops of iodine be added to solution of starch, a 
deep-blue color is at once produced. This blue color disappears 
when the liquid is heated to 90°, and reappears on cooling. If 
a few drops of a neutral solution of calcium chloride be added 
to the liquid, dark-blue flakes are precipitated, coiistituting 
what is called iodide of starch. It is starch dyed by iodine. 





riG.128. 



Metamorphoses of Starch — Dextrin. — When long heated 
to 100° starch is converted into soluble starch, which yields a 
blue color with iodine (Maschke). 

Between 160 and 200° it is converted into a body which is 
very soluble in water, and the solution of which is not colored 
by iodine. This solution strongly turns the plane of polariza- 
tion to the right ; hence the name dextrin given to this body, 
which is regarded as isomeric with starch, (C*^H^°0^)". A very 
concentrated solution of dextrin has the appearance of a solu- 
tion of gaim. It is used as a mucilage for labels, and for the 
preparation of immovable surgical dressings. 

Alcohol added to a solution of dextrin precipitates the latter 
substance in the form of flakes. Subacetate of lead does not 

49* 



582 ELEMENTS OF MODERN CHEMISTRY. 

precipitate dextrin, a character which permits the hitter body 
to be distinguished from gum arabic. 

When starch is boiled with water containing a few per cent, 
of sulphuric acid, it is first converted into dextrin, then into 
glucose. It is generally considered that the dextrin is formed 
by a simple molecular transformation of the elements of thQ 
starch, and that the glucose is then produced by the simple 
fixation of one molecule of water. 

Starch. Glucose. 

According to Musculus, this is not the case ; but soluble 
starch is the result of a metameric transformation of starch, 
and subsequently is converted into dextrin and glucose by a 
true decomposition. • 

Q18H30Q15 _|_ JJ2Q ^ C''H^°0^*' C«H^'0« 
starch. Dextrin. Glucose. 

By the prolonged action of the acid, the dextrin itself is 
converted into glucose. 

The transformation of starch into dextrin and saccharine 
matter (maltose) takes place easily under the influence of a 
peculiar ferment which is developed in grain during germina- 
tion, and to which the name diastase has been given. It 
may be obtained by precipitating aqueous extract of malt by 
alcohol. 

If starch be triturated with one and a half times its weight 
of concentrated sulphuric acid, avoiding an elevation of tem- 
perature, and the mixture be left to itself for half an hour and 
alcohol then added, a substance is precipitated which is soluble 
in water and assumes a rich blue tint by the action of iodine. 
It is sohihle starch (Bechamp). 

Starch dissolves abundantly in monohydrated nitric acid, 
and water precipitates from this solution a white substance, 
which, after washing and drying, constitutes xi/loidin. It is 
mononitro-starch, and results from the substitution of a group 
NO'^, for one atom of hydrogen in starch. 

Starch. Xyloidin. , 

Xyloidin burns with deflagration when heated to 180°. 



INULIN — GLYCOGEN — GUMS. 583 

INULIN. 

C6H10O5 

Tliis body also is largely diffused tlirougliout the vegetable 
kingdom. It exists in the roots of the elecampane i^liiala 
hckniiun), chicory, and Spanish chamomile, in the bulbs of 
colchicum, the tubers of the dahlia, in the Jerusalem arti- 
choke, etc. It may be extracted from the tubers of the dahlia 
by reducing them to a pulp and washing the latter in a sieve 
under a stream of water. The milky liquid which passes 
through deposits the inulin, which consists of granules analo- 
gous to those of starch. It swells in cold water, in which it 
is very slightly soluble. It is very soluble in boiling water, 
which again deposits it in a pulverulent form on cooling. The 
aqueous solution turns the plane of polarization to the left. 
It is not colored blue by iodine, which communicates to it a 
fugitive, yellow-brown tint. 

By long boiling with water, or by the action of dilute acids, 
inulin is converted into levulose. 

GLYCOGEN. 

C6H10O5 

This body, isomeric with cellulose and starch, exists in the 
animal economy. Claude Bernard discovered it in the liver, 
and afterwards in the placenta. It exists also in many organs 
during the fuetal life. Nearly pure glycogen may be obtained 
by adding a large quantity of crystallizable acetic acid to a cold 
and concentrated decoction of liver. It is also precipitated 
when alcohol is added to an aqueous decoction of liver. In a 
pure state, it is a white, amorphous powder. When dried in 
the air, it has the composition C^H^'^0'' (E. Pelouze). At 100'' 
it loses one molecule of water. 

With water it forms an opalescent liquid. Alcohol and 
ether do not dissolve it. Boiling with dilute acids converts it 
into glucose. Iodine communicates to it a violet or brown-red 
color. 

GUMS. 

By the names gums and mucilages are understood certain 
substances existing everywhere in the vegetable kingdom, and 
which dissolve or swell up in water, giving a mucilaginous 



584 ELEMENTS OP MODERN CHEMISTRY. 

consistence to the liquid. The gums proper arc distinguished 
from the mucihiginous substances, which are not really soluble. 
Both furnish mucic and oxalic acids when treated with nitric 
acid. Grum furnishes at the same time a small quantity of 
tartaric acid. 

Gum Arabic. — Gum arabic is identical with Senegal gum. 
It flows naturally from different species of acacia. It dissolves 
abundantly in cold water and is precipitated from its solution 
by alcohol. Fremy considers that it is composed essentially of 
the calcium and potassium salts of an acid which he designates 
as giunmic acid (^arahui). 

When dried at 100°, the latter body has the composition 
indicated by the formula C^'^H'^-'O^^ It is very soluble in 
water, and its solution rotates the plane of polarization to the 
left. 

When heated to 120-150°, it becomes insoluble in water 
and is converted into metagummic acid. According to Fremy, 
the gum of cherry- and plum-trees is a mixture of gummates, 
which are soluble in cold water, and insoluble metagummates. 
The metagummates are insoluble in water, but when boiled 
with that liquid are transformed into soluble gummates. 

Subacetate of lead forms an abundant white precipitate in 
solutions of gum arabic. 

When gum arabic is boiled with dilute sulphuric acid, it is 
converted into a mixture of two saccharine substances ; one is 
uncrystallizable, the other crystallizes in large, colorless rhombic 
prisms, having a sweet taste, and fusible at 1G0°. It is called 
arahinose. It reduces the cupro-potassic solution and is not 
fermentable. It is isomeric with glucose. 

Gum Tragacanth. — This gum flows from the Astragalus of 
the Levant and of Persia. Bassora gum is derived from a spe- 
cies of cactus. Both contain a mucilaginous matter insoluble in 
water, but which swells up in that liquid, forming a transparent 
jelly. This matter is ha.ssorin. With nitric acid, it yields much 
mucic acid. When boiled with dilute sulphuric acid, it is readily 
converted into crystallizable glucose. 

CELLULOSE. 

C6H10O5 

This name is given to the matter which forms the walls of 
young vegetable cells, and which is deposited, mixed with other 



CELLULOSE. 585 

matters, in the older cells, particularly in ligneous fibre. The 
pith of the elder and of jEsch^nomene paludosa., cotton, old 
linen, and paper are almost pure cellulose. 

In ligneous fibres, in wood, the cellulose is permeated by 
various Ibreign substances, among which Payen has distin- 
guished the incrusting matter which thickens the tissues and 
gives them rigidity. Among the others are nitrogenous mat- 
ters, resins, various coloring matters, etc. With these organic 
substances in the ligneous fibres, are united the mineral ele- 
ments which are found more or less modified in the ashes. 

Old linen and cotton serve for the preparation of pure 
cellulose. Such materials are boiled with a weak solution of 
potassium hydrate, washed, and successively exhausted with a 
solution of chlorine, acetic acid, alcohol, ether, and water, and 
dried at 100°. The insoluble product which remains after this 
treatment is considered as pure cellulose. 

Properties. — Cellulose is a diaphanous, white solid, of a 
density of 1.25 to 1.45. It is insoluble in water, alcohol, 
ether, and the dilute acids and alkalies. It dissolves in the 
cupro-ammoniacal liquid which is obtained by dissolving cupric 
hydrate or carbonate in a small quantity of concentrated am- 
monia, or better, by dissolving metallic copper in ammonia in 
contact with the air (Schweizer). 

When submitted to dry distillation, cellulose leaves a residue 
of carbon and yields numerous gaseous and liquid products. 
The gas obtained by the distillation of wood is used for illu- 
minating purposes in some localities. The liquid product 
ordinarily separates into two layers, one of which is aqueous 
and contains acetic acid, wood-spirit, acetone, etc. ; the other is 
insoluble in water and constitutes wood-tar. 

When cellulose, charpie for example, is sprinkled with con- 
centrated sulphuric acid and the mass is rapidly triturated, a 
viscous mass, having but little color, is obtained ; it contains, 
independently of a compound of sulphuric acid and cellulose 
(sulpho-ligneous acid), substances which result from the dis- 
integration of the cellulose. Accordingl}^, as the action of the 
acid is more or less prolonged, a substance is obtained which is 
insoluble in water and colored blue by iodine and consequently 
analogous to starch, or a soluble matter analogous to dextrin 
(Bechamp). When water is added to this viscous mass and 
the whole is submitted to a prolonged ebullition, fermentable 
glucose is formed (BraconnotJ. 
z* 



58G ELEMENTS OP MODERN CHEMISTRY. 

C6JJ10O5 _|_ H^O = C'^Hi^O^ 

Cellulose. Glucose. 

When paper is dipped into a cold mixture of sulphuric acid 
with half its volume of water, and is then carefully washed and 
dried, a semi-transparent matter is obtained which has a certain 
rigidity, and is similar to parchment, in luspect (Figuier and 
Poumarede, Hofniann). It is called vegetable parchment. 

A cold solution of chloride of zinc converts cellulose into an 
amyloid matter which is colored blue by iodine ; if heat be 
applied, the whole is dissolved and glucose is formed. 

When charpie is heated with a concentrated solution of cal- 
cium hypochlorite (chloride of lime), a very violent reaction 
takes place, and torrents of carbon dioxide are evolved. 

Gun-Cotton. — When carded cotton is immersed for half a 
minute in monohydrated nitric acid, and then rapidly washed 
in a large quantity of water and allowed to dry in the air, a 
substance is obtained which possesses all the exterior appear- 
ances of cotton, but is very inflammable and burns suddenly 
without residue. It is gun-cotton, or pyroxi/Un, which was 
discovered by Schonbein in 1847. 

In its preparation, the monohydrated nitric acid may be 

advantageously replaced by a mixture of one volume of fuming 

nitric acid and three volumes of sulphuric acid. Pyroxylin 

seems to be a mixture of dinitrocellulose and trinitrocellulose. 

Q6JJ10Q5 C^H^NO'^'O^ CTF(NO'')-'0^ 

Cellulose. Dinitrocellulose. Trinitrocellulose. 

Gun-cotton looks like cotton, but is more harsh to the touch 
and sometimes has a light yellowish tint. It burns with a 
sudden flash, leaving no residue, and produces a great volume 
of gaseous products consisting of carbon monoxide, carbon 
dioxide, nitrogen dioxide, etc., and vapor of water. Gun-cotton 
is insoluble in water, alcohol, ether, chloroform, and the cupro- 
ammoniacal solution. It is more or less soluble in a mixture 
of alcohol and ether, and the solution is employed in surgery 
and photography under the name collodion. When pyroxylin is 
lieated with a concentrated solution of ferrous chloride, nitrogen 
dioxide is disengaged, and cellulose is regenerated (Bechamp). 

GLUCOSIDES. 

The glucosides are complex compounds, which break up 
under various conditions, fixing the elements of water and 



GLUCOSIDES. 587 

yieldinp: glucose and other bodies, just as the compound ethers, 
in fixing the elements of water, are decomposed into alcohols 
and acids. 

This definition seems to relate the glucosides to the com- 
pound ethers, a relation with seems legitimate, since it has 
been shown by the experiments of Berthelot that glucose has 
the function of a polyatomic alcohol. 

Various immediate principles of vegetable origin can be 
classed as glucosides. We may mention particularly the fol- 
lowing : 

glucosid::s. formulas. origin. 

Amygdalin .... C'^OH-^^NOii bitter almonds. 

Salicin 01^111*^0^ willow and poplar bark. 

Populin C^'^il'^'O'^ bark and leaves of the aspen. 

Phloridzin .... C^'H-i^Oio bark and roots of fruit-trees. 

Arbutin C^'^W^O'' leaves of the ArctosUqihylos uva nrsi. 

Convolvulin .... C^ilisooie ] . , 

Jalappin C^^HSGO^e | jalap-root. 

Esculin C2in2iOi^ bark of India chestnut. 

Fraxin C2UP0Oi7 bark of the ash. 

Daphnin C^^H^^O^^ Daphne alpiuci, Dajihne mezereum. 

Quinovin C^OII+SQ^ bark of 67/ /»a ho fa. 

Tannin C-^'H'^^Qn oak-bark, nut-galls, etc. 

Among all of these bodies, we will only consider amygdalin, 
salicin, populin, phloridzin, and tannin, or tannic acid. 

Amygdalin, C''°H^^NO^^ — This body is extracted from the 
cake of bitter almonds, and it deposits from its alcoholic solu- 
tion in crystals containing two molecules of water. Its aqueous 
solution allows it to crystallize in quite large crystals contain- 
ing three molecules of water. 

Amygdalin is very soluble in water and in boiling alcohol. 
Its aqueous solution rotates the plane of polarization to the 
left. 

By the action of dilute aci(0" amygdalin is decomposed into 
hydrocyanic acid, benzoyl hydride, or benzoic aldehyde (oil of 
bitter almonds), and glucose. 

C^oH^^NO^^ _l_ 2H^0 = C'H'^0 + CHN -f 2C«H^^0« 

Amygdalin. Benzoic Hydrocyanic Glucose, 

aldehyde. acid. 

The same decomposition takes place by the action of water 
and a peculiar ferment which is contained in both bitter and 
sweet almonds, and which is called emuhin^ or iiynaptase. It 
is a nitrogenized matter, soluble in water, and only acts on 
amygdalin in presence of water. It is well known, jndeed, tliat 



588 ELEMENTS OP MODERN CHEMISTRY. 

bitter almonds only develop tlie odor of prussic acid when 
moistened with water. 

Salicin, C'*I^^O^ — Salicin exists already formed in the bark 
of the willow and poplar. Wohler discovered its existence in 
castoreum. It may be prepared by exhausting willow-bark 
with boiling water, concentrating the liquid and digesting it 
with litharge. The solution is then filtered and evaporated to 
a syrupy consistence ; the salicin deposits in a few days. 

It occurs in small scales, or brilliant needles, soluble in water 
and alcohol and insoluble in ether. Its aqueous solution turns 
the plane of polarization to the left. 

Salicin dissolves in sulphuric acid, forming a red liquid. 

By the action of a solution of emulsin (the nitrogenous mat- 
ter of almonds), it breaks up into a neutral body called salige- 
nin, and glucose. 

Salicin. Saligeuin. Glucose. 

Dilute sulphuric and hydrochloric acids decompose it by 
the aid of heat into saliretin and glucose. These bodies will 
be described farther on. 

When salicin is fused with potassium hydrate, hydrogen is 
disengaged, and salicylic and oxalic acids are formed. 

By the action of a mixture of potassium dichromate and 
sulphuric acid, salicin yields carbon dioxide, formic acid, and 
an oxidized oil, which is the hydride of salicyl or salicylic alde- 
hyde, C^H^O'^ (Piria). 

Populin, C'^H'^'^O^ -I- 2H20.— Braconnot discovered this sub- 
stance in the bark and leaves of the aspen (^Pojndus tremida). 
To extract it, those substances are exhausted with boiling water, 
the decoction is precipitated by subacetate of lead, filtered, and 
the filtrate evaporated to a sjjrupy consistence. On cooling, 
the populin is deposited as a crystalline precipitate. When 
properly purified, it occurs in very fine, silky, colorless needles. 
Its taste is sweet ; it is but slightly soluble in water, more 
soluble in alcohol. By the action of dilute acids, it is decom- 
posed into benzoic acid, saliretin, and glucose ; the latter two 
products result from the decomposition of salicin, so that popu- 
lin appears to be a combination of benzoic acid and salicin. 

(.20^2^0^ _j_ H'^0 = (yWO' + Q''W^O' 

Populin. Benzoic acid. Salicin. 

Phloridzin, C^^H^^O'" + 2H^0.— This substance exists in 



GLUCOSIDES. 589 

the bark of apple, pear, plum, and cherry trees, and principally 
in the roots of fruit-trees. It may be extracted by boiliiiii; the 
roots with water, decanting the boiling solution, concentrating 
it, and allowing it to stand in a cool place. The phloridzin 
deposits on cooling, and may be puriticd by recrystallization 
after decolorizing it with animal chnrcoal. 

When pure, it forms colorless, silky needles, having a bitter 
taste, and an after-taste which is sweet. It is scarcely soluble 
in cold water, but dissolves abundantly in boiling water and 
in alcohol. The alcoholic solution turns the plane of polariza- 
tion to the left. 

Dilute sulphuric and hydrochloric acids decompose it into 
phloretiu and glucose. 

(.21H24Q10 _|_ JJ2Q ^ C^5JJU05 _|_ Q'^H^'^O'^ 

Phloridzin. Phloretin. Glucose. 

Phloretin is a white substance which crystallizes in little 
scales, slightly soluble in water and very soluble in alcohol. 
When phloretin is heated with potassium hydrate, it breaks up 
into phloretic acid and pliloroglucin. 

(;,i5jjuo^ -f- H-'O =. C^H^oQ^ + C^H«0^ 

Phloi-etin. Phloretic acid. Phloroglucin. 

Phloroglucin forms large crystals having a sweet taste. 

Tannin, or Tannic Acid, C^^H^^O". — The names tannins 
and tannic acids are applied to certain slightly acid compounds 
which are largely diffused in the vegetable kingdom, and which 
have two important properties : they precipitate solutions of 
gelatin and albuminous matters, and produce a bluish or 
greenish-black color with the ferric salts. The most important 
of these compounds, the tannin of oak bark, or quercitannic 
acid, is a glucoside. By the action of dilute acids it is decom- 
posed into gallic acid and glucose (Strecker). 

Tannin exists in oak bark, in sumac, and in large quantities 
in nut-galls, which are excrescences developed by the sting of 
an insect on the leaves and branches of the Quercus infectoyia. 

It is prepared by introducing coarsely-powdered nut-galls into 
a percolator, and exhausting them with ordinary commercial 
ether. The ethereal solution which passes through is collected 
in a flask, and in the course of a day separates into two or 
sometimes three layers. The lower layer is a very concen- 
trated, aqueous solution of tannin. It is separated and dried 

60 



590 ELEMENTS OP MODERN CHEMISTRY. 

in a hot-air oven. The tannin remains as a light, bulky mass, 
having a yellowish color. 

Tannin is a colorless, amorphous solid, having a very astrin- 
gent taste. It is very soluble in water, less soluble in alcohol, 
insoluble in pure ether. 

It melts when heated, and between 210 and 215° it dis- 
engages carbon dioxide and yields pyrogallol, C^H*^0^, which 
volatilizes. xV black residue remains (^metagallic acid). 

On contact with the air, the aqueous solution of tannic acid 
absorbs oxygen, disengages carbon dioxide, and deposits gallic 
acid. This transformation takes place more rapidly when oak 
tannin is boiled with dilute sulphuric or hydrochloric acid. 

c-^H^-o^' _j_ 4H2Q ^ sc^ipo^ + en^^o^ 

Tannin. Gallic acid. Glucose. 

The researches of H. Schiff seem to show that tannin, prop- 
erly speaking, is not a glucoside but is digalUc acid, C^^H^^O", 
that is, an acid derived from two molecules of gallic acid by the 
subtraction of one molecule of water. By fixing the elements 
of water, a molecule of tannin would form two molecules of 
gallic acid. 

CujjioQs _|. H^O = 2C'H60^ 

Digallio acid. Gallic acid. 

A solution of tannic acid produces with ferric salts a bluish- 
black precipitate, which constitutes ink. Tannin does not color 
ferrous salts, but the mixture soon blackens on exposure to the 
air by absorbing oxygen. 

Tannin is employed in medicine as an astringent. Nut-galls, 
which are very rich in tannin, are used for the manufacture of 
ink. A good ink may be prepared by the following receipt: 
One kilogramme of powdered nut-galls is exhausted with 14 litres 
of water ; the solution is filtered, and a solution of 500 grammes 
of gum arabic is first added, then a solution of 500 grammes of 
ferrous sulphate (green vitriol). The mixture is well stirred up, 
and then exposed to the air until it has acquired a fine black color. 



AROMATIC COMPOUNDS. 

The compounds which we have studied thus fiir are rich in 
atoms of hydrogen. Most of them are saturated or derived 
from saturated compounds. The hydrocarbons of the series 
C"H'^"+^ the alcohols C"H'"+"^0, the fatty acids C"H'^"0-, are 



AROMATIC COMPOUNDS. 591 

of these classes of compounds the most rich in hydrogen that 
are known ; they belong to what is called the fatty series. But 
there are other compounds which possess, like the preceding, 
the characters of hydrocarbons, alcohols, and acids, in which 
the relation between the atoms of carbon and of hydrogen is not 
the same. The atoms of the latter element decrease in num- 
ber in proportion to those of the former. These relations may 
be understood by a glance at the following formulae : 

Cioil'^2 decane. CioiP^O dccvl hvdrate. 

Cioir-'O dec.vlene. C^ni^^O iiiiiit caniphor. 

C'OH'S menthene. CiOHi»0 Borneo camphor. 

C10I116 turpentine. CioiPfiO ordinary camphor. 

C10H14 cymene. CioiP^O thvraol. 

C10H8 naphthalene. CioiP'^0 cuminic aldehyde. 

A large number of these unsaturated compounds belong 
or are related to those aromatic substances which are called 
essences or essential oils. Hence the name aromatic com- 
pounds^ which has been given to all of these bodies containing 
but little hydrogen. 

The most interesting of the hydrocarbons of the aromatic 
series is benzol, which is now obtained in large quantities from 
coal-tar. It is as important by reason of the applications which 
it has received in the arts as on account of the theoretical con- 
siderations which attach to it. Kekule has made it the centre 
of the aromatic series which would include, in a limited sense, 
only the derivatives of benzol. In a w^ord, the latter body is 
the nucleus of all the aromatic compounds. 

Kekule's theory considers that the 6 atoms of carbon of 
benzol form a closed chain, each being bound to its neighbors, 
on one side by one, and on the other by two bonds of saturation. 
One atom of hydrogen is attached to each of these carbon atoms. 

H 

k 

H-C C-H 

I II 
H-C C-H 

Benzol.* 

* In this formula, the connecting lines indicate the saturation of the 
atomicities; the double lines indicate the exchange of two atomicities 
between two neighboring atoms of carbon. 



592 ELEMENTS OF MODERN CHEMISTRY. 

Very numerous and very different aromatic compounds are 
derived by the substitution of different elements or groups for 
the hydrogen atoms in the molecule of benzol, that molecule 
forming, so to speak, the nucleus of all the aromatic com- 
pounds. 

1. If one atom of hydrogen be replaced by chlorine or bro- 
mine, monochlorobenzol or monobromobcnzol will result, these 
compounds being also called chloride and bromide of phenyl. 

Q6JJ6 C'H^Cl C^H^Br 

Benzol. Monochlorobenzol. Moliobioniobenzol. 

2. If one atom of hydrogen be replaced by the group hy- 
droxyl (OH), phenol, or phenyl hydrate, is formed. The sub- 
stitution of two hydroxy! groups for two atoms of hydrogen 
produces the oxyphenols ; that of three groups OH for three 
atoms of hydrogen produces phloroglucin (page 618). 

f\TT /'OH 

C6H6 C6H3.0H C6II^<^!J C6H3^0H 

Benzol. Phenol. Oxyphenol and Phloroglucin and 

its isomerides. its isomerides. 

3. The substitution of one or more groups (NO')' for one 
or more atoms of hydrogen gives rise to the nitro-derivatives. 

C6H6 C6H5-N02 C6H*<Jj^!J 

Benzol. Nitrobenzol. Dinitrobenzol. 

4. The substitution of the group (NH'^) for one atom of 
hydrogen produces phenylamine, or aniline ; that of two groups 
NH^ for two atoms of hydrogen yields phenylene-diamine. 

C6H6 CHP^m ^*'^^'<NH2 

Benzol. Phenylamine (aniline). Phenylene-diamine 

and its isomerides. 

5. If one or more atoms of hydrogen in benzol be replaced 
by as many methyl groups, CH^, the superior homologues of 
benzol are obtained. 

C6II6 = C6H6 benzol. 

Cni» = C«H5-CH3 toluol (racthylbenzol). 

C8H10 ^^ C''H*<^pjj3 xylol and isomerides (diraethylbonzols). 

^CH3 
C^IP^ __ C^'IP:::— CIP mesitylcne and isomerides (trimeth^'lbenzols). 

^CH3 
C12II18 _ C(CH3)6 hexamcthylbenzol. 

One ethyl group can replace one atom of hydrogen in ben- 



AROMATIC COMPOUNDS. 59^3 

zol, and ethylbenzol, which is isomeric with dimethylbenzol, 
would result. 

C6II5-C2II5 C6II*<^,J|3 

Ethylbenzol. Dinietlijibciizol. 

There are many instances of such isomerism, and they re- 
ceive the same interpretation. 

One atom of hydrogen in benzol may be replaced by a propyl 
group, C'lP, and l)ropyl benzol, which is isomeric with trimethyl- 
benzol, is the result. 

One atom of hydrogen may be replaced by an ethyl group 
and another by a methyl group, and the new compound would 
be ethyl-mcthylbenzol, isomeric with propylbenzol and with tri- 
methylbenzol. 

C6H5-C3II7 C6H4<pjif C«H3— CH3 

^11 ^^-CH3 

Propylbenzol (cumene). Ethyl-methylbenzol. Trimethylbenzol. 

These alcoholic radicals which are thus substituted for the 
hydrogen of benzol, constitute, according to the expression of 
Kekule, lateral chains, which are grafted, so to speak, on the 
benzol nucleus or principal chain. 

6. The aromatic acids, properly speaking, result from the 
substitution of one or more carboxyl gToups, CO. OH = CO^H, 
for one or more hydrogen atoms in the benzol nucleus. 



C6H6 


C6H5-C02n 


Mi*<coS 


CH\\conif 


C6(C0'^II)6 


Benzol. 


Benzoic acid. 


Phthalic acid 
and isomerides. 


Trimesic acid 
and isomerides. 


Melllc acid. 



7. In the homologues of benzol, the substitution of 01, Br, 
OH, NH^, CO^H, etc., for hydrogen, may take place either in 
the benzol nucleus or in the lateral chain : isomeric compounds 
are thus formed. 

a. By substitution of one atom of. chlorine for an atom of 
hydrogen in toluol, two isomeric compounds, C'H^Cl, may be 
obtained. In one, the chlorine will be attached to the lateral 
chain ; in the other, it will be attached to the benzol nucleus, 
as is the group CH^ itself. 

C6II5-CH3 C6IP-C1I2C1 C6H4<^j^3 

Toluol. Benzyl chloride. Chlorotoliiol. 

h. The phenols result from the substitution of OH for an 
atom of hydrogen in the nucleus. If this substitution take 
place in a lateral chain, an aromaiic alcohol, isomeric with the 
corresponding phenol, is obtained. 

50* 



594 ELEMENTS OF MODERN CHEMISTRY. 

C6II5-CH3 C«H5-CII2(OH) C6II4<J]J^^3 

Tolmil. Benzylic alcohol. Cresol. 

c. The substitution of a carboxyl group, CO'^H, for an atom 
of hydrogen in the benzol nucleus of toluol, C^tP-CH^, pro- 
duces the aromatic acids, toluic acid, and its isomerides ; if, 
however, the carboxyl replace a hydrogen atom in the lateral 
chain, CH'\ alpha-toluic acid, isomeric with the preceding acids, 
results. 

C6H5-CH3 C6H*<^^^,y C6H5_Cn2-C02H 

Toluol. Toluic acids. a-toluic acid. 

d. When two groups OH are substituted for two atoms of 

hydrogen in the principal chain, oxyphenols are formed. 

/CH3 
C6H3--OH 

Orcin. 

e. The substitution of the group NH^ for one atom of hydro- 
gen in the principal chain, on the one hand, and in the lateral 
chain, on the other, produces isomeric alkaloids. 

C6H5-CH(NH2) C6H*<^^3'^ 

Benzjiamine. Toluidiue. 

8. This is not all ; the lateral chains may be grafted at dif- 
ferent points of the benzol nucleus by substitution for the dif- 
ferent hydrogen atoms. Their positions and their relative dis- 
tances from each other are the causes of numerous isomerisms. 

It is important to understand the principle of this isomer- 
ism. Let us consider the most simple case, that in which 
two atoms of hydrogen are replaced by two other monatomic 
atoms or monatomic groups. Such compounds are the di- 
substituted derivatives of benzol, and experiment has shown 
that there are three di-substituted derivatives of each kind. 

Thus there are three hydrocarbons containing ^wo groups 
CH'\ each substituted for one atom of hydrogen in benzol ; 
three phenols, each containing two groups OH ; three acids, 
each containing one group CO'^H, and one group OH, substi- 
tuted each for one atom of hydrogen, and three acids, each 
containing two carboxyl groups substituted for two atoms of 
hydrogen. Indeed, this substitution may take place in three 
different ways. The six carbon atoms forming a closed chain 
and a hydrogen atom being attached to each carbon, the re- 



AROMATIC COMPOUNDS. 



595 



placement of two atoms of liydroticn may affect two adjoin- 
ing atoms of carbon, or two atoms of carbon separated by a 
third atom of carbon which still retains its H, or lastly, two 
carbon atoms which are separated by two other carbon atoms, 
each of which still retains its H. The relative positions of the 
groups being different in each case, it results that the molecules 
present different structures and are consequently isomeric. The 
following examples will explain this kind of isomerism. 

O/Y/io-derivatives are those in which the hydrogen of two 
adjacent carbon atoms is replaced ; ??ie^6t-derivatives are those 
in which the two carbon atoms affected are separated by a third ; 
para-derivatives are those in which the two carbon atoms are 
separated by two others. 



< 
1 


CH3 


OH 


OH 


C02H 


A 

HC C-CH3 

1 II 
HC CH 


A 

HC C-OH 

1 H 

HC CH 


^C^ 
Hc''' '^C-C02H 
h6, liH 
C 


HC C-C02H 
HC CH 


6 


H 


H 


H 


H 


o 


Orthoxylol. 


Orthofliphenol 
(pyrocatechin). 


Orthoxybenzoic 

acid 

(salicylic). 


Orthoplithalic 

acid 

(phthalic). 



CB 


cm 


OH 


OH 


C02H 


> 

< 
> 

1 


A 

Hc' ^CH 
HC C-CH3 

H 


A 

HC CH 

1 If 
HC C-OH 

%' 
H 


^C^ 

HC'^' ^CH 

HC C-C02H 

\' 
H 


A 

RC CH 

HC C-C02H 

C 
H 


E 


Metaxylol. 


Metadipheuol 
(resorciii). 


]\Ietoxybenzoic 

acid 

(oxybeuzoic). 


Metaphthalic acid 
(isophthalic). 


a 


CH3 


OH 


OH 


C02H 


t 

< 

> 

ft 


HC CH 

h6 '6k 

c 

CH3 


HC^ CH 
HC CH 

^C^ 

6r 


A 

HC CH 

HC CH 

y 

C02H 


HC CH 
HC CH 

'Y 

C02H 


p-i 


Paraxylol. 


Paradiplvenol 
(hydroquinone). 


Paroxybenzoic 
acid. 


Paraplitlialic acid 
(teiaphthalic). 



596 ELEMENTS OF MODERN CHEMISTRY. 

These indications will suffice to illustrate the class of isomer- 
ides under consideration. With the tri-substituted derivatives 
of benzol, theory foresees and experiment has demonstrated the 
existence of still more numerous isomerides, but we cannot 
dwell on them here. 

Two very important hydrocarbons are now considered as 
directly related to benzol. They are naphthalene, C^°H^, and 
anthracene, C^^H^". 

Naphthalene is formed by the union of two benzol nuclei, 
two atoms of carbon being common to each nucleus (Erlen- 
meyer). 

Anthracene results from the union of two benzol nuclei by 
the intermediation of two carbon atoms, which are themselves 
combined together, each by one atomicity, and each of which 
is combined with one atom of hydrogen (Graebe). 

These ideas are indicated in the following graphic formulae, 
which express the reciprocal relations between the atoms of 
carbon and hydrogen, but not their real positions in space. The 
latter might be better indicated by a polyhedral form. 

H H H H H 

,C C C C H C 

HC CH HC C CH HC C-C-C CH 

HC CH h6 C CH HC C-C-C CH 

V 'c' ^c'^ • ^'-^ J' '^'^ 

H H H 



C H C 
H H 



Benzol. Naphthalene. Anthracene. 

We must with these brief indications conclude the considera- 
tion of the principles of Kekule's theory, which includes very 
many compounds. These are the aromatic compounds in the 
strict sense of the word. Before undertaking their study, we 
will briefly describe oil of turpentine and some of the bodies 
allied to it. 

OIL OF TURPENTINE AND ITS ISOMERIDES. 

A large number of hydrocarbons are known having the com- 
position C^°H^^. Some are the natural products which consti- 
tute the whole or part of the numerous essential oils. Others 
are the products of art. 

Among the first are the oils of turpentine, lemon, orange, 
bergamot, orange-flower, juniper, savin, lavender, cubebs, co- 
paiba, elemi, pepper, cloves, etc. 



TURPENTINE. 507 

These oils arc li(iuids ; some of them are mixed with oxy- 
genized solid bodies which are deposited in time, and which 
were formerly designated as stearoptcncs. 

They are obtained by distilling the vegetable products which 
contain them with water, for, although the boiling-points of 
these oils are between 150 and 200°, they distil readily with 
aqueous vapor, and collect in the form of a layer on the sur- 
face of the condensed water. 

The more ordinary process consists in passing a current of 
steam through the plants or aromatic vegetables. For this 
purpose they are placed on a diaphragm, M (Fig. 129), which 




(C^ 



(0) 



M 



Fig. 129. 

is fixed above the bottom of an ordinary still. The head of 
the still is then adjusted, connection is made wath a condenser, 
and a current of steam is passed in by the tube TT'T", which 
penetrates into the still. The steam carries with it the essen- 
tial oil, which diffuses in it by virtue of 
the high tension of the vapor of these oils at 
100°. The mixed vapors rise into the head 
of the still and condense in the condensing 
worm. The condensed water, generally 
clouded by little drops of the essential oil, 
is received in a vessel of peculiar form, 
which is called a Florentine receiver. It is 
shaped like an ordinary flask (Fig. 130), 
having at its bottom a tube which curves 




upwards, in the form of a swan's neck, and 

the upper part of which is but little below ^^' 

the mouth of the flask. As the condensed water and oil collect 

in this ingenious apparatus, the oil separates and floats on the 

water ; as the distillation continues, the liquid rises not only in 



598 ELEMENTS OP MODERN CHEMISTRY. 

the flask, but in the lateral tube, until the water, which is 
always in large excess, reaches the level of the curved neck 
and flows off" alone, the lighter oil accumulating in the flask. 

Among the essential oils whose composition is represented 
by the formula C^*'1P'^, the most important is oil of turpentine, 
which is obtained by distilling the turpentine of commerce with 
water. Turpentine is a mixture of resin and essential oil, and 
flows from incisions cut in the trunks of trees of the genera 
Pinns, Abies, Picea, Larix. 

When this resinous substance is distilled with water, the oil 
passes over and the resin remains ; the latter is called colo- 
phanjij, or rosin. 

Turpentine. — Bordeaux turpentine, which comes from the 
Puius maritlma (Pinus Puiasfer), yields, by distillation with 
water, an essential oil which boils at 156°, and turns the plane 
of polarization to the left. Density at 0°, 0.877. 

Australine, or English oil of turpentine, which comes from 
the Pinus Ausfnilis, has the same boiling-point as the preced- 
ing, but turns the phxne of polarization to the right. Density 
at 16°, 0.864 (Berthelot). American oil of turpentine, derived 
from Pinus paliistris, is also dextrogyrate. 

Metamorphoses of Oil of Turpentine. — 1. When exposed 
to the air, oil of turpentine gradually absorbs oxygen, becomes 
yellow and partly resinified. This slow oxidation is due to the 
production of ozone, with which the oil becomes charged ; it 
then possesses oxidizing properties (page 61). 

2. Concentrated nitric acid oxidizes oil of turpentine with 
such energy that the mixture sometimes takes fire. When 
boiled with dilute nitric acid, it forms teraphthalic acid, 

(^6jj4^ one of the isAmerides of phthalic acid (Cailliot). 

3. When a mixture of alcohol, nitric acid, and oil of turpentine 
is left to itself for some time, the latter substance fixes the ele- 
ments of three molecules of water and is converted into a crys- 
tallized solid body, Q'^K^O'' + H'^0, called ferpin. 

4. When oil of turpentine is mixed with 2V i^^ weight of 
concentrated sulphuric acid, and the mixture is agitated, it is 
converted into an isomeric hydrocarbon, tcrehene, which boils 
at 156°, and a polymeric hydrocarbon, C'-^^H'", which boils 
between 310 and 313° (H. Deville). By reason of the re- 
ducing action which the oil of turpentine exerts on the sul- 
phuric acid, and which produces sulphurous oxide and water, 



TURPENTINE. 599 

two atoms of hydrogen are removed from the molecule C'"!!'^, 
and, independently of terebene, a certain quantity of CJ/mcnc, 
C'nV\ is formed (Riban). 

cm'' -f so^H'^ =-- c'^H^^ + so'^ + 2ir-'o 

5. The hydracids combine with oil of turpentine. Three com- 
pounds of turpentine and hydrochloric acid are known. A solid 
hydrochloride, C"'H"^.HC1, is deposited from cooled oil of tur- 
pentine by the action of gaseous hydrochloric acid, and is called 
arttjicial camphor. It is levogyrate, or dextrogyrate, accord- 
ingly as it has been prepared from turpentine or australine. 
The crystals are deposited from a very acid, colorless liquid, con- 
taining a licjuid combination of turpentine and hydrochloric acid. 

When oil of turpentine is left for a month in contact with 
very concentrated hydrochloric acid, a dihydrochloride is 
formed, C'"H^^2HC1. It is a solid body, and is identical or 
isomeric with the artificial camphor of oil of lemon, obtained 
by passing hydrochloric acid gas into oil of lemon. 

6. Antimony trichloride transforms oil of turpentine into a 
solid polymeride, tetraturpentine. 

Terebene. — Terebene, which has already been mentioned, 
boils at 156°, like its isomeride, oil of turpentine, from which 
it differs by being optically inactive ; it forms no crystalline 
hydrate corresponding to terpin, and it never yields a dihy- 
drochloride. Like turpentine, it forms a crystalline monohy- 
drochloride when subjected to the action of hydrochloric acid 
gas (Riban). 

Camphenes. — When dextro- or levo-artificial camphor is 
heated to between 200 and 220° with sodium stearate, HCl 
is removed, and the camphor is transformed into a solid, crys- 
tallizable hydrocarbon, fusible at 146°, and boiling at 160°. 
It is camphene, and is optically active in the same direction as 
the hydrochloride, from which it is derived. 

The sodium stearate here acts as a feeble alkali ; when it is 
replaced by sodium benzoate, inactive camphene is set at lib- 
erty. The camphenes yield only monohydrochlorides by the 
action of hydrochloric acid gas (Berthelot). 

The hydrochlorides of turpentine, terebene, and camphene 
are isomeric ; the first is almost undecomposable by water at 
100°, the second loses all of its hydrochloric acid by the action 
of boiling water, and it is the same with the third, which, how- 
ever, regenerates solid camphene (Iliban). 



GOO ELEMENTS OF MODERN CHEMISTRY. 

Isoturpentine. — When oil of turpentine is heated to 300°, 
it is transformed into a new isomeride, wliich is active and 
levogyrate : it is isoturpentine, and boils towards 176°. Den- 
sity at 0°, 0.859. At the same time as isoturpentine, meta- 
turpentine is formed, C'^^W\ boiling at 360°. 

Terpilene. — This is another isomeride of oil of turpentine, 
and boils at the same temperature. It is obtained by removing 
all of the hydrochloric acid from the dihydrochloride, C'"!!^^. 
2HC1, by the action of either sodium (Berthelot) or aniline 
(Lauth and Oppenheim). 

It is characterized by the fact that it yields a dihydrochlo- 
ride with great ease by the action of gaseous hydrochloric acid, 
and does not form a monohydrochloride. 

Citrene, C^"H^^ — This hydrocarbon is contained in oil of 
lemon, together with an oxygenized body. It is a colorless 
liquid, having an agreeable odor. It boils at 173-174°. Den- 
sity at 15°, 0.85. 

Citrene unites readily with hydrochloric acid, producing a 
crystalline dihydrochloride of citrene, C^°H^^2HC1, fusible at 
14°. 



ORDINARY CAMPHOR, OR LAUREL CAMPHOR. 

C10H16O 

Camphor exists in all of the organs of the Laurus camphora, 
a tree of China, Japan, and the islands of the Bay of Sundy. 
When the wood is chipped and distilled with water, the cam- 
phor volatilizes and condenses in rice-straw, with which the 
heads of the stills in which the operation is conducted are filled. 
The product thus obtained in the form of small crystals is re- 
fined by sublimation in glass vessels heated on a sand-bath. 

A camphor identical with laurel camphor is deposited from 
the oil of Matricaria partheniiim when the latter is cooled. 
It is matricaria camphor. 

Camphor forms a semi-transparent, crystalline mass. Its 
odor is strong and aromatic ; its taste, bitter and burning. It 
melts at 175°, and boils and distils without alteration at 204°. 
Its density at 0° is 1.0. At ordinary temperatures, the ten- 
sion of its vapor is so great that it sublimes spontaneously in 
the vessels in which it is kept. 

Camphor is almost insoluble in water; when thrown in 



CAMniOR. 601 

small fragments on the surface of that li(jiiid, it executes gyra- 
tory movements. It dissolves in alcohol and ether, and the al- 
coholic solution rotates the plane of polarization to the right. 

Camphor is inflammahle, and burns with a smoky flame. 
The following are its principal reactions : 

■ 1. When heated with phosphoric anhydride, or with chloride 
of zinc, it loses the elements of water and is converted into a 
hydrocarbon called cymene. 

Camphor. Cyiuene. 

2. Camphor appears to be an aldehyde. Although it does 
not fix hydrogen directly, it can nevertheless be converted into 
a compound, C^'^H^^O, which is borneol, or Borneo camphor. 
This is accomplished by the action of sodium, which replaces 
the hydrogen of a portion of the camphor, forming a sodium- 
camphor, while the displaced hydrogen is fixed upon another 
portion of camphor (Baubigny). 

According to this reaction, corroborated by the inverse re- 
action, which will be indicated farther on, the same relations 
seem to exist between borneol and camphor as between alco- 
hol and aldehyde. 

C^H^O C^H«0 

Aldehyde. Alcohol. 

Camphor. Borneol. 

3. When camphor is heated for a long time with an alcoholic 
solution of potassium hydrate, it is decomposed into an acid 
and an alcohol, which is borneol (Berthelot). 

2C'm''0 -\- KOH = C^^H^^KO^ + C/m^'O 

Camphor. Potassium camphate. Borneol. 

4. When vapor of camphor is passed over soda-lime, heated 
to about 300°, the sodium salt of campliolic acid is obtained 
(Delalande). 

(110JJ16Q _|_ ^^QH ^ C^^H^'NaO^ 

Camphor. Sodium campholate. 

5. When camphor is subjected to the action of aqueous 
hypochlorous acid, it is converted into mo?iocJiloro-camj)hor, 
C^"H^^C10, which constitutes a colorless, crystalline mass, 
slightly soluble in water, freely soluble in alcohol and ether, 
and fusible at 95°. 

2a 51 



602 ELEMENTS OF MODERN CHEMISTRY. 

6. By the action of bromine on camphor at 100 or 120°, 
monohromo - camphor^ C^°FP^BrO, and dihromo - camplior^ 
C'°H^^Br-0, are formed. These bodies crystallize in colorless 
prisms. The first fuses at 70°, the second, at 114°. 

A bromide of camphor, C^°H^'^OBr"^, is also known; it is 
formed by the action of bromine on a solution of camphor in 
chloroform. It is a crystalline body which decomposes spon- 
taneously, especially by the action of liuht, losing hydrobromic 
acid and being converted into monobromo-camphor. 

7. Camphor absorbs hydrochloric acid gas, forming an oil 
which is instantly decomposed by water, regenerating camphor. 
Cold nitric acid dissolves it, forming an oily liquid which is de- 
composed by water, camphor being precipitated. 

8. When camphor is boiled with nitric acid, it is oxidized 
and converted into camphoric acid. 

Q10JJ16O + 0^ ^ C^^H^^O* 

Camphor. Camphoric acid. 

BORNEOL, OB BORNEO CAMPHOB. 

C10H18O 

This camphor is extracted from the Dryohalanops aroinatica, 
a tree which grows in the Sundy Islands. Berthelot has ob- 
tained it by the action of an alcoholic solution of potassa on 
ordinary caniphor. It occurs in small, colorless, transparent, 
and friable crystals. Its odor recalls at the same time that of 
camphor and that of pepper. Its taste is burning. It melts 
at 198°, and boils at 212°. It turns the plane of polarization 
to the right. It is insoluble in water, but dissolves readily in 
alcohol and in ether. When treated with cold, fuming nitric acid, 
it loses H^, and is converted into ordinary camphor, C^^H^'^O. 

BENZOL. 
C6H« 

This important body was discovered in 1825 by Faraday. 
Mitscherlich obtained it by heating benzoic acid with an excess 
of lime. 

C^H^O'^ = CO^ + C'H^ 

Eenzoic acid. Benzol. 

It is now obtained in large quantities from coal-tar by dis- 
tilling the latter body. The more volatile products contain the 



BENZOL. G03 

benzol, which is purified by fractional distillation. That which 
pjisses below 85° is principally benzol, and the latter crystal- 
lizes out when the liquid which passes between 80 and 85° is 
cooled to — 5°. The crystals are collected and separated by 
expression from the product remaining licpiid. They constitute 
pure benzol.* Berthelot has recently made the direct synthesis 
of benzol by exposing acetylene to a temperature near redness. 
3C^H^ = C'W 

Acetylene. Benzol. 

Benzol is a colorless, strongly refracting liquid. At 0°, it 
solidifies to crystals which melt at 5.5°. It boils at 80.5°. 
'It is insoluble in water, but dissolves in alcohol and ether. It 
is inflammable, and burns with a bright, smoky flame. 

When long agitated with fuming, or even ordinary sulphuric 
acid, it dissolves, forming phenylsulphurous acid. 

riienylsulpliurons acid. 

When heated to 275 or 280° for twenty-four hours with 80 
to 100 parts of concentrated hydriodic acid, benzol is converted 
into hexane, C^H^^, iodine being set free. 

Action of Chlorine and Bromine on Benzol. — In sun- 
light, benzol can absorb directly six atoms of chlorine, forming 
benzol hexacJiIorkle, C'^H'^CP, crystallizable in brilliant plates. 
Another product of the action of chlorine on benzol is mono- 
chlorohenzol, C^ffCl, a liquid, boiling between 135 and 137°. 

An excess of bromine in sunlight converts benzol into a solid 
bromide, C^H«Br«. 

Monohyomohenzol, C^H^Br, may be made by mixing benzol 
and bromine in the proportion of one molecule of the first to 
two atoms of the second, and leaving the mixture to itself for 
a week at the ordinary temperature. It is then washed, first 
with water then with potassa, and distilled. Monobromobenzol 
boils at 152-15-1°. When heated with sodium, it yields to the 

cm' 

latter its bromine, and a hydrocarbon C^"^II^" = i ., called 

\j -H. 
diphenyl^ is obtained. 

Dihromohenzol, C^H^Br^, is readily formed by the action of 
an excess of bromine on benzol. It crystallizes in beautiful 
prisms, fusible at 89°. It boils at 219°. 

•••■ Benzol must not be confounded with the benzine derived from petro- 
leum, which is a saturated hydrocarbon. 



604 ELEMENTS OF MODERN CHEMISTRY. 

Nitrobenzol, ^^[^(NO^). — If benzol be poured in small 
portions into monohydrated nitric acid, and water be added to 
the mixture, an oily, yellow liquid separates, constituting nitro- 
benzol. 

C'H^ + HNO^ = WO + C'HXNO^) 

It is benzol in which one hydrogen atom is replaced by the 
group (NO')'. 

Nitrobenzol is a yellowish liquid, having a strong odor of 
bitter almonds. It boils at 205*^, and solidifies at 3°. It is 
employed in perfumery under the name essence of Mirhane. 

By the action of reducing agents, such as hydrogen sulphide, 
ammonium sulphide, tin and hydrochloric acid, or iron-filings 
and acetic acid, nitrobenzol is converted into aniline or phenyl- 
amine. 

C'HXNO^) + 3H2 = 2ffO + C«H^(NH^) 

Nitrobenzol. Aniline. ' 

When long heated with very concentrated nitric acid, nitro- 
benzol is transformed into metadinitrobenzol, C*^H*(NO'^)"'^, which 
forms long, right rhombic prisms, fusible at 118^. 

Azoxybenzol, Azobenzol, Hydrazobenzol. — There are other 
products of the reduction of nitrobenzol, independently of 
aniline. When nitrobenzol is acted upon by alcoholic potas- 
sium hydrate, or by sodium amalgam in presence of water, the 
reduction is less complete, and it is converted successively into 
azoxybenzol and azobenzol (Zinin). 

C6H5-X 

2C6H5-N02 + 3H2 = 3H20 + i \0 

Nitrobenzol. Azoxybenzol. 

C6H5-N 
2C6H5-N02 + 4H2 = 4H20 + ii 

C6H5_N 
Nitrobenzol. Azobenzol. 

Azoxybenzol forms long, yellow prisms, fusible at 36°, very 
soluble in alcohol and ether. 

Azobenzol forms large, red crystals, fusible at 66.5°. It 
boils without decomposition at 293°. It is insoluble in water, 
but dissolves in alcohol and ether. 

In the presence of reducing agents, such as hydrogen sul- 
phide, ammonium sulphide, or sodium amalgam and water, 
both of the preceding bodies fix hydrogen and are converted 
into hydrazobenzol. 



CYANOBENZOL — PHENOL. 605 



C6I15-N 


C6II5-NII 


II + 112 




C6II5_N 


^ C61P-NII 


A.zobenzul. 


Hydrazobonzol. 



The latter body crystallizes in tables, fusible at 131°, almost 
insoluble in water but soluble in alcohol and ether. When 
submitted to dry distillation, it breaks up into azobenzol and 
aniline. 

2Qi2jji2js^2 ^ C'^H'ON^ _|_ 2C«H^NH2 

Hydrazobeuzol. Azobenzol. Auiline. 

CYANOBENZOL. 

(phenyl cyanide, benzonitrile.) 

C6H5.cn 

This body is formed in various reactions, particularly in the 
destructive distillation of hippuric acid, and by the dehydration 
of benzamide by phosphoric anhydride. 

C<^H^-CO.NH^ — H-'O = C^H^-CN 

Benzamide. Benzonitrile. 

It is a colorless oil, which boils at 191°. When heated with 
the alkalies, it yields benzoic acid and ammonia. 

C«H^-CN + 2H20 = C'H^-CO^H + NH^ 

Benzonitrile. Benzoic acid. 

PHENOL, OR PHENYL HYDRATE. 

C6H5.0H 
This body bears the same relation to benzol that wood-spirit 



does to marsh gas. 




CH4 

Methane. 


CH3.0H 

Methyl hydrate. 


C6H6 
Benzol. 


C6H5.0H 

Phenol. 



It was discovered in coal-tar by Runge, who named it car- 
bolic acid. Laurent demonstrated that it plays the part of an 
alcohol. Indeed, it presents points of resemblance with the 
monatomic alcohols, but it diifers from them by its acid char- 
acter, on account of which it is sometimes called phenic acid. 

Preparation. — Large quantities of phenol are obtained from 
coal-tar, from which it is separated by distillation. That part 
which passes between 150 and 200° is collected apart and 

51* 



606 ELEMENTS OF MODERN CHEMISTRY. 

mixed with a saturated solution of potassium or sodium hy- 
drate to which soHd potassa or soda is added. A cr3'stalline 
phenate of potassium or sodium is formed ; it is dissolved in 
boilinir water, the insoluble oil which floats is separated, and 
the alkaline solution is neutralized with hydrochloric acid. 
The phenol separates ; it is washed with a small quantity of 
water, dehydrated with calcium chloride, and rectified. The 
distilled product is cooled to — 10°, and the crystals which are 
deposited are allowed to drain out of contact with the air. 

Phenol may be made artificially from benzol by a process 
which is applicable to the preparation of all the phenols. It 
consists in treating; benzol with fuming or even ordinary 
sulphuric acid. Phenylsulphurous acid is formed ; this is 
diluted with water to separate the excess of hydrocarbon, and 
the solution is neutralized with chalk ; calcium phenylsulphite, 
which is soluble, and sulphate, which is insoluble, are formed. 
The calcium phenylsulphite is converted into sodium phenyl- 
sulphite by double decomposition with sodium carbonate, and 
after evaporation and desiccation, the sodium phenylsul})hite is 
fused in a silver crucible with an excess of potassium hydrate. 
The mass is exhausted with water, and the alkaline solution is 
decomposed by hydrochloric acid. The phenol separates and 
is dried and purified by distillation (Dusart, Wurtz, Kckule). 

The decomposition of sodium or potassium phenylsulphite 
is expressed in the following equation : 

C^ff.SO^K -f KOH = C^IP.OH + K^SO^ 

Potassium plienylsulphite. riieiiol. Potassium sulphite. 

There is another very simple synthesis of phenol. In pres- 
ence of aluminium chloride, benzol absorbs oxygen directl}' and 
phenol is formed. 

C'W -f =: eH«0 

This reaction is one of the most unexpected and most in- 
teresting applications of a general method of synthesis discov- 
ered by Friedel and Crafts (see page G19). 

Properties of Phenol. — Phenol is a solid, crj^stallizing in 
long, colorless needles, fusible at 85°. It has a peculiar, char- 
acteristic odor, and an acrid, burning taste. It boils at 180°. 
It is slightly soluble in water, but dissolves readily in concen- 
trated acetic acid. It possesses antiseptic properties. 

Although phenol is neutral to litmus-paper, it forms definite 
combinations with the alkalies. When it is mixed with a very 



TRINITROPHENOL. ()()7 

concentrated solution of potassium lij'drate, a crystalline mass 
is obtained wliieh constitutes potassium phenate, C'lI'.OK. 

Plios])horus pert-liloride converts it into phenyl chloride, 
identical with monochlorobenzol. 

C'FP.oii + POP = c«ir"'Ci -f pocp + iici 

riieiiol. Phenyl chloride. 

The following remarkable reaction of phenol was first noticed 
by lleimer and Tiemann, When it is heated with cldoroform 
and an excess of sodium hydrate, in the ])r()})ortion of one 
molecule each of phenol and chloroform and four molecules of 
alkali, it is converted into salicylic aldehyde (salicyl hydride). 

C^PP.ONa + 3NaOH -f CHCP= C^H^O'^Na + 3NaCl + 2H^0 

Sodium Sodium salicylite. 

phenate. 

The compound C'lPO'^Na is the sodium compound of sali- 
cylic aldehyde, into which it is converted by hydrochloric acid. 

TRINITROPHENOL. 

(picric acid.) 

C6H2(NO'^)3.0H 

When phenol is boiled with concentrated nitric acid, it is 
converted into trinitrophenol. 

C^H^OH -h 3HN0^^ = 3W0 + C'tP(NO-)lOH 

This body has long been known, and is generally called j^icric 
acid. It deposits from boiling water in lemon-yellowy crystal- 
line plates, only slightly soluble in cold water. Its taste is very 
bitter. With the bases it forms crystallizable salts, which deto- 
nate with violence when heated. 

Potassium picrate, C*'H'^(NO'^)^.OK, crystallizes in long, yel- 
low needles, soluble in 14 parts of boiling water and in 250 
parts at 15°. It explodes violently when heated. 

Picramic Acid. — When a current of hydrogen sulphide is 
passed through an alcoholic solution of picric acid saturated 
with ammonia, sulphur separates and the picric acid is con- 
verted into jyic^'ciniic acid (A. Girard). 

C6H•^(NO^|3.0H + 3H2S == 2H-^0 + S^ -f C6H2(N02)2(NH-^)OH 

Picric acid. Picramic acid. 

The hydrogen sulphide partially reduces the picric acid, and 
one of the three groups (NO'"^) is thus converted into a group 



608 ELEMENTS OF MODERN CHEMISTRY. 

(NH^). Picramic acid is dinitro-amido-phenol, that is, phenol 
in which two atoms of hydrogen are rephiecd by two groups 
(NO'), and a tliird atom of hydrogen by the group NH"-. 

When acetic acid is added to a hot acjueous sohition of the 
ammonium salt of picramic acid, the picramic acid is deposited 
in fine red needles. 

AURIN (ROSOLIC ACIDS). 

When 1^ part of phenol is heated with 1 part of oxalic 
acid and 2 parts of sulphuric acid, it is converted into a color- 
ing-matter, which was first described under the name rosolic 
acid, or coralline-yellow. The same body or analogous bodies 
may be obtained by means of the rosanilines (see farther on). 
Indeed, it has been recognized that there are several homolo- 
gous bodies having the properties and the constitution of roso- 
lic acid. 

Rosolic acid made from pure phenol contains C'^H^^O'^ and 
is called aurin (Dale and Schorlemmer). It occurs in very 
brilliant, red, anorthic prisms having a blue or green reflection. 
It corresponds to a rosaniline, C'^H^V.NH'^)^ (pararosaniline). 

To ordinary rosaniline and its superior homologue, chrysoto- 
luidine (see farther on), correspond two other rosolic acids, supe- 
rior homologues of aurin. The following formulae indicate the 
relations which exist between these bodies: 

C^^H"(0H)3 C^9H"(NH2)^ 

Aurin. Inferior homologue of rosaniline. 

Rosolic acid. Ordinary rosaniline. 

Aurin is used in dyeing. When it is heated to 180° with 
an alcoholic solution of ammonia, it is converted into a bright- 
red coloring matter, noticed by Persoz, and employed in dyeing 
under the name coralline-red. 

ANILINE, OR PIIENYLAMINE. 

C6H7N = C6H5.NH2 

Aniline was discovered by Unverdorben among the products 
of the distillation of indigo, and was extracted from coal-tar by 
Runge. It is now prepared artificially by a process discovered 
by Zinin. This process consists in converting benzol into ni- 



ANILIDES. GOO 

trobenzol, and subjecting the latter to the action of reducing 
agents (see nitrobenzol). 

Iron and acetic acid are advantageously used to accomplish 
this reduction (Bechanip). 

Aniline is a colorless, mobile, highly-refracting liquid, having 
a peculiar, unpleasant smell, and an acrid, burning taste. It 
is a little heavier than water. It boils at 184.8°. When ex- 
posed to the air, it becomes brown and is eventually resinified. 

Aniline is almost insoluble in water, but mixes in all pro- 
portions with alcohol, ether, and the fatty and volatile oils. 

It does not restore the blue color to reddened litmus-paper, 
but nevertheless possesses the character of an alkaloid, for it 
forms well-defined salts with the acids. 

Reactions. — 1. If a nitrate and sulphuric acid be added to 
aniline, a red color is produced. 

2. If a few drops of aniline be poured into an excess of sul- 
phuric acid, and a small quantity of potassium dichromate be 
added, a magnificent blue color is developed, which changes to 
violet on the addition of water. 

3. A solution of calcium hypochlorite (chloride of lime) 
added to aniline produces a beautiful violet tint. 

4. When a solution of an aniline salt is heated with cupric 
chlorate, an intense black color is developed (Ch. Lauth). 

These reactions are applied in the arts in the preparation of 
coloring matters of incomparable richness. The most impor- 
tant of these matters is rosanilme, or /uchsine, which will be 
described farther on. 

Salts of Aniline. — These are obtained by saturating aniline 
by the acids. 

Aniline hydrochloride^ C^H^N.HCl, forms colorless needles, 
which are fusible, and can be distilled without alteration ; they 
are very soluble in water and in alcohol. Platinic chloride pre- 
cipitates from the solution fine yellow needles of a chloro-plati- 
nate, (C'^H^N.HCl)TtCl\ 

Aniline oxalate^ (C'^H^N)^C"'^II^O*, crystallizes from water in 
hard, thick prisms. When heated, it loses the elements of 
water, and is converted into oxanilide. 

ANILIDES. 

By the action of heat, the aniline salts lose the elements of 
water, and form compounds analogous to the amides, and which 
2a* 



610 ELEMENTS OF MODERN CHEMISTRY. 

Gerhardt named amlides. When aniline oxalate is heated, it 
is converted into oxanilide, which is no other than oxamide 
in which two atoms of hydrogen are replaced by two phenyl 
groups, (C^H^). 

C202 ) C202 ) 

H2 I N2 (C61i5j2 I N2 

H2 J H2 J 

Oxamide. Phenyl oxamide (oxanilide). 



C2H30 ) C2H:^0 ) 

H [ N C6Ii5 > N 

Hj HJ 

Acetamide. Phenylacetamide (acetanilide.) 



DIAZOBENZOL COMPOUNDS. 

Nitrous acid exerts an energetic action upon aniline and the 
analogous bases ; it is indicated here because it presents a great 
generality and gives rise to remarkable bodies, which are called 
diazo-co mp o mids. 

When a current of nitrous gas is passed into a saturated so- 
lution of an aniline salt, such as the nitrate, crystals of diazo- 
henzol nitrate are deposited. 

C^H^N.HNO^^ + HNO^ = 2W0 + C'^H^NINO"' 

Aniline nitrate. Diazobenzol nitrate. 

This body is formed by the substitution of one atom of nitro- 
gen for three atoms of hydrogen in aniline nitrate. 

C6H5-NH2.HNOS aniline nitrate. 
C6H5-N=N-(N03) diazobenzol nitrate. 

It forms long, colorless prisms, very soluble in water, slightly 
soluble in alcohol, and insoluble in ether. It explodes violently 
by heat or by percussion. This salt and its congeners present 
two remarkable reactions. When heated with water, they dis- 
engage nitrogen, and are converted into phenols. 

C^H^NINO^ 4- H^O = C^H^OH + N' + HNO^ 

When they are boiled with absolute alcohol, they are reduced 
to hydrocarbons, nitrogen being disengaged and the aicohol 
being transformed into aldehyde. 

C^H^NIHSO* + OWO == C^H^O + Q'W + N^ + H^SO* 

Diazobenzol sulphate. Aldehyde. Benzol. 

When aniline is added to an aqueous solution of diazobenzol 



ROSANILINE. Gil 

nitrate, a diazo-compound is obtained wliich is more complex 
than the preceding and is called diazoamulohcnzol. 

C^H^N-XNCP) -f NH-'.CTP := C"IP-N-'-NII.C«IP + UNO' 

Diazoboiizol nitrate. Aniline. Diazoaiuidobenzol. 

The same body is formed when a current of nitrogen tri- 
oxide is passed into a cooled alcoholic solntloii of aniline. It 
forms brilliant, golden-yellow scales, fusible at 91°. It ex- 
plodes at a higher temperature. 



ROSANILINE AND ITS DERIVATIVES. 

C20pil9;^T3 

This magnificent red coloring matter is obtained by heating 
aniline to 150 or 160° with arsenic acid, which acts in this case 
as an oxidizing agent. The solid product of the reaction is 
dissolved in water, and the filtered solution is treated with solu- 
tion of sodium hydrate ; the rosaniline which was combined 
with arsenic acid is precipitated. It is then dissolved in acetic 
or hydrochloric acid, and the salt so formed is crystallized. 
It separates in magnificent crystals which present a green re- 
flection, like the scales of cantharides, and dissolve in alcohol 
with a rich purple color. 

The rosaniline formed in this reaction results from the oxida- 
tion of the aniline, and toluidine (see fiirther on), which always 
exists in commercial aniline. 



C^H'N -]- 2C"H9N + 0^ == C^°H^»N^ -f 3H-'0 

Aniline. Toluidine. Rosaniline. 

In the preparation of rosaniline, arsenic acid, the use of 
which, is dangerous, has been replaced by another oxidizing 
agent, which is nitrobenzol. The latter acts by virtue of the 
group NO'^ which it contains (J. Persoz). This improvement 
has been introduced in France by Coupier, and in Germany by 
Meister, Lucius, Briining. 

Properties of Rosaniline. — The methods of preparation 
just indicated furnish the salts of rosaniline, such as the hydro- 
chloride, which is the rich coloring matter known as fuchsine. 
The free base is obtained by treating a hot, saturated solution 
of the hydrochloride with an excess of soda. The rosaniline 
separates as an almost colorless, crystalline precipitate. It is a 
triacid base which requires three molecules of hydrochloric 



612 ELEMENTS OF MODERN CHEMISTRY. 

acid for its saturation. It is curious that free rosaniline is 
colorless and occurs in small crystals. 

The monohydrochloride of rosaniline, C-''H'^X^HC1 (fuch- 
sine), forms dark-colored, rhombic tables, having a splendid 
green reflection. It is but slightly soluble in water, but dis- 
solves readily in alcohol, forming an intense purj^le solution. 

The trihydrochloride, C'^H^^'NiaiiCl, forms yellow-brown 
needles which lose hydrochloric acid when heated or when dis- 
solved in water. 

Kosaniline and its salts present two important reactions : 

1. When a salt of rosaniline is treated with reducing agents, 
such as nascent hydrogen (zinc and hydrochloric acid), the 
base fixes two atoms of hydrogen and is converted into Icu- 
cauiluie, C'^'^H^^N'^, a wdiite powder slightly soluble in water. 

2. By the action of nitrogen trioxide, rosaniline is converted 
into a diazo-derivative which yields rosolic acid when boiled 
with water (pages 608 and 610). 

Constitution of Rosaniline. — According to Hofmann, the 
formula C'-''H^'*N^ represents the composition of rosaniline. It 
is exact, but it has been recognized that the products known 
under the name fuchsine contain several isomerides (Rosen- 
stiehl), 'and it is known, besides, that there are several homo- 
logues of rosaniline. Without dwelling on the subject, we may 
mention the following bodies : 

C^^Ri^N^ pararosaniline (Fischer). 
C20II19N3 rosaniline. 
C211121N3 chrysotoluidine. 

There exist also corresponding leucanilines containing two 
more atoms of hydrogen. 

Hofmann has attributed to the rosaniline C^^H^^N^ the con- 
stitution expressed by the formula 

2(C^HTfN' 
H^3 

According to him, it is a triamine, containing at the same 
time a diatomic group phenylene, C^H*, and two diatomic 
groups C^H^ 

Recent researches tend to modify this view. E. and 0. 
Fischer consider that this rosaniline is a triamine, C'"!!'"* 
(NH'^/, derived from a hydrocarbon C"-''H'^, and that para- 



ROSANILINE. G13 

rosaniline is a triamine, C^'H"(Nrr^)'', derived from a hydro- 
carbon, C'^H^*. By subjecting tlie corresponding leucanilines 
to the action of nitrous anhydride, and reducing the diazo- 
compounds thus formed by alcohol, these chemists obtained 
the hydrocarbons C'"''H^® and C^^H"'', which were again con- 
verted into leucanilines, and then, by oxidation of the latter, 
into rosanilines. 

We may add that the hydrocarbon C'^H^'^, which is solid 
and fusible at 93°, is triphenylmethane, that is, marsh-gas, in 
which three atoms of hydrogen are replaced by three phenyl 
groups. 

Methane. Triphenylmethane. 

Coloring Matters derived from Rosaniline. — When rosan- 
iline is heated with ethyl iodide, three atoms of hydrogen are 
replaced by three ethyl groups, and this tnethyl-rosaniline 
yields with the acids a magnificent violet color, known as Hof- 
mann's violet. 

Triphenyl-rosaniluie, in which three atoms of hydrogen are 
replaced by three phenyl groups, C^H^, is formed when rosani- 
line is heated with an excess of aniline. This reaction, in 
which ammonia is disengaged, was discovered by Girard and 
de Laire. 

(.20^192^3 _^ sC^HlNir = Q''W\Q'WfW + 3NH^ 

Kosaniline. Aniline. Triphenyl-rosaniline. 

The hydrochloride of triphenyl-rosaniline is of a magnificent 
blue color, and is known as Lyons hlne (Ch. Girard and de 
Laire). The following formulae show the interesting relations 
which exist between rosaniline and its ethyl and phenyl deriv- 
atives : 

Rosaniline. Triethyl-rosanilinc. Triphenyl-rosaniline. 

(Base of Hofniann's violet.) (Base of Lyons blue.) 

We may mention among the derivatives of rosaniline, Paris 
violet and the aniline greens, particularly the beautiful color- 
ing matter known as night-green, because it retains its rich 
green tint in artificial light. 

Paris violet, which has been for some years manufactured 
by Poirrier, is a splendid color, produced by the oxidation of 
methylaniline or dimethylaniline. 

52 



614 ELEMENTS OF MODERN CHEMISTRY. 

C6H5 ) C6H3 ) 

C113 In cun n 

HJ CIPJ 

Methylaniline. Dimetbylaiiiline. 

Ch. Lauth realizes this oxidation, or rather dehydrogena- 
tion, by heating methyhaniline with cupric chloride. The 
reaction is complex, and, according to Hofmann and Martius, 
gives rise to trimcthyl-rosaniline. 

When heated with methyl chloride, the base of Paris violet 
fixes two molecules of that compound, forming a combination 
of trimethyl-rosaniline and methyl chloride. This combination 
constitutes night-green. 

Dicliloioniethylate of trimethyl-rosaniline 
(night-green). 

DIPHENYLAMINE. 

C6H5) 

C12H11N = C«H5 V N 
HJ 

This body is derived from ammonia by the substitution of 
two phenyl groups for two atoms of hydrogen. It is formed 
in various reactions, of which the most interesting was discov- 
ered by Girard and de Laire. It consists in heating aniline 
hydrochloride to 256° with aniline. Ammonia is disengaged, 
and diphenylamine hydrochloride is formed. 

C6H5 ) C6H5 ) C6H5 ^ 

H [ N.HCl + H y N = C61I5 I N.HCl + NH^ 

HJ IlJ HJ 

Free diphenylamine forms crystals fusible at 54°. It boils 
at 310°. It is insoluble in water, but dissolves in alcohol, 
ether, benzol, and petroleum. Its odor recalls that of oil of 
rose. 

When heated with a mixture of oxalic and sulphuric acids, 
it yields a splendid blue color, soluble in water, and known as 
dipheni/lamine blue (Girard and de Laire). 

OXYPHENOLS. 

C6H602 

Three isomeric bodies having the composition C^H^O^ ^= 

OH 
(^6jj4^ are known ; they are derived from benzol by the 

substitution of two hydroxyl groups for two atoms of hydro- 



RESORCIN. G15 

gen. These three bodies are oxyphenol, or pyrocatechin, resor- 
cin, and liydroquinoiie. 

Pyrocatechin. — Tliis body is so named because it was first 
obtained ])y tlie destructive distillation of caoutchouc. It is 
also produced by the distillation of jiuni kino and various tan- 
nins which produce a green color witli ferric salts. Pyroca- 
techin is a solid body, ver}' soluble in water and alcohol, very 
slightly soluble in ether ; it crystallizes from its aqueous solu- 
tion in rectangular prisms, belonging to the orthorhombic sys- 
tem. It melts at 111.8°, and sublimes below that temperature 
in brilliant, colorless plates. It boils between 240 and 245°. 
Its odor is strong and excites sneezing. It has the character 
of an acid, like phenol itself It dissolves in the alkalies and 
in the alkaline carbonates. When exposed to the air, these 
solutions become colored, first green, then brown and black. 
An aqueous solution of p3'rocatechin produces a deep-green 
color with ferric chloride, which changes to dark-red on the 
addition of an alkali. 

Resorcin. — This body, which is the homologue of orcin, 
C^H^O'^, is formed when certain gums, such as galbanum, 
asafoetida, gum ammoniac, sagapenum, etc., are fused with 
potassium hydrate (Hlasiwetz and Barth). It is extracted 
from the fused mass by dissolving the latter in water, super- 
saturating with sulphuric acid, filtering, and agitating the fil- 
tered solution with ether, which dissolves the resorcin. After 
having driven ofi" the ether on a water-bath, a residue is ob- 
tained which is distilled : the resorcin sublimes and condenses 
in radiated crystals. 

Oppenheim and Yogt obtained resorcin by fusing chloro- 
phenyisulphurous acid with potassium h3'drate. The former 
body is obtained when chlorobenzol is treated with sulphuric 
acid. 

C6H5C1 + H2S0* = H20 + C6H*<^^^^ 

CLlorobenzol. Chloroi)henyl- 

sulphurous acid. 

C6H4<^J^^^ + 2K0H = KCl + K2S03 + C6H* I qjJ 

Potassium chlorophenyl- Resorcin. 

sulphite. 

Resorcin forms colorless, prismatic or tabular crystals. It 
melts at 110°, and boils at 271°. . It is very soluble in water, 
alcohol, and ether. 



GIG ELEMENTS OF MODERN CHEMISTRY. 



QUINONE AND HYDROQUINONE. 

Quinone, CH^O^ — This remarkable body, discovered by 
Woskresensky, is a product of the oxidation of quinic acid, 
which exists in cinchona bark. It may be obtained by dis- 
tilling that acid with a mixture of manL>;anese dioxide and 
sulphuric acid. The mass swells up and disengages vapors of 
quinone, which condense in the receiver in brilliant, golden- 
yellow needles. They are pressed between folds of filter-paper 
and purified by resublimation. 

Quinone crystallizes in long, brilliant, transparent needles of 
a golden-yellow color. It is very soluble in cold water, and 
more soluble in alcohol and ether. It melts at 115.7° to a 
yellow liquid, which at 115.2° solidifies to a crystalline mass. 
It sublimes at ordinary temperatures, emitting pungent vapors 
which excite tears. 

Chlorine converts it into a trichloro-derivative, C^HCPO^, 
crystallizable in small, yellow prisms, fusible at 1G-1:-166°. 

When treated with a mixture of potassium chlorate and 
hydrochloric acid, quinone is converted into tetrachloroquinone, 
C^CPO^, better known as cldovaUne. This name was given by 
Erdmann, who first obtained this body by the action of chlorine 
on indigo, of Avhich the Portuguese name is anil. The same 
body is formed by the action of a mixture of potassium chlorate 
and hydrochloric acid on a great number of aromatic com- 
pounds, such as phenol, picric acid, salicylic acid, salicin, isatine, 
etc. Tetrachloroquinone forms pale-yellow scales, having a 
pearly, metallic lustre. When gently heated, it sublimes with- 
out fusing, and leaves no residue. It is insoluble in water and 
almost insoluble in cold alcohol, but dissolves in boiling alcohol 
and separates on cooling in golden-yellow scales. 

Hydroquinone, C^IPO^. — This body is formed by the action 
of reducing agents, such as nascent hydrogen, hydriodic acid, 
or sulphurous acid, on quinone. 

(TWO'' + H^ == C^H'^O^ 

Wbhler, who discovered it, found it also among the products 
of the dry distillation of quinic acid. 

Hydroquinone crystallizes in beautiful, transparent, and col- 
orless, right rhombic prisms. It has no odor ; its taste is 
sweetish. It dissolves in 17 parts of water at 15°, and is very 



QUINONE AND IIYDROQUINONE. ()17 

soluble in alcohol and ether. It melts at 177.5°, and solidifies 
at 165°. When uontly heated, it sublimes in l^rilliant plates, 
like those of sublimed benzoic acid. It partially decomposes 
when abruptly heated. When its vapor is passed through a 
tube heated to dull redness, it breaks up into quinone and 
hydrogen. Various oxidizing agents, such as chlorine, ferric 
chloride, nitric acid, silver nitrate, and potassium dichromate, 
transform it into a substance which deposits in magnificent 
green needles, having a metallic reflection. It is qumhydvone 
or green liijdroquinone^ C^'^H^'^O^ a combination of quinone and 
hydroquinone. 

Constitution of Quinone and Hydroquinone. — According 
to Graebe, these bodies are allied to benzol, from which the first 
is derived by the substitution of two atoms of oxygen for two 
atoms of hydrogen ; but as the two atoms of oxygen represent 
four atomicities, of which two only are employed in replacing 
H'^ in benzol, the other two serve to bind together the two 
atoms of oxygen. The couple (0"-0")" can indeed play the 
part of a diatomic group. In the formation of hydroquinone, 
these atoms of oxygen separate from each other and each fixes 
one atom of hydrogen, so that two hydroxyl groups are formed 
and substituted each for one atom of hydrogen in benzol. The 
following formulije express these relations : 

C6H6 C6H^< ^ C6H4<^Og 

Benzol. Quinone. Hydroquinone. 

This view is generally adopted, but it is not established with 
certainty. It may be that each atom of oxygen is united by 
both of its atomicities to a carbon atom. In this case it would 
be necessary to admit that the constitution of the benzol nucleus 
is modified, in that the double bond uniting two carbon atoms 
would be resolved into one. 



H 


H 




H 


A 

[C CH 

c 


.A 

HC C-0 

Hfc ii-0 

c 


or 


.A 

HC C^ 

HC a 

C 


H 


H 




H 


Benzol. 


Quinone. 




Quinone. 



Bodies anologous to quinone and hydroquinone have been 
obtained from naphthalene and anthracene. 

52^ 



G18 ELEMENTS OF MODERN CHEMISTRY. 

PHLOKOGLUCIN. 

(J6H6O3=06H3(OH)3 

PhVoroglucin and its isomeride pyrogallol are trioxyplienols, 
and represent benzol in which three atoms of hydrogen are 
rephiced by three hydroxy! groups. The relations jjetween 
phloroglucin, oxyphenol, and phenol, are the same as tliosc 
between glycerin, propylglycol, and propyl alcohol. 

foil f^II 

C3H7.0H C3H6 ^ij C3H5 \ OH 

(OH I Qjj 

Propyl alcohol. Propj'lglycol. Glycerin. 

f OTT f OH 

C6H5.0H C6H* j ^g C6H3 j OH 

Phenol. Oxyphenol. Phloroglucin. 

Phloroglucin was discovered by Hlasiwetz, who obtained it 
by heating phloretin (page 589) with a very concentrated solu- 
tion of potassa. It is also formed in many other reactions, 
especially when gum-kino, gamboge, and dragon's-blood are 
fused with potassium hydrate. 

Phloroglucin crystallizes in hard, rhombic prisms, having a 
very sweet taste. It is quite soluble in water, alcohol, and 
ether. Its aqueous solution is neutral. Its ethereal solution, 
evaporated upon a microscope slide, deposits prisms in tangled, 
tree-like forms which are very characteristic. 

The crystals deposited from ether are anhydrous, while those 
formed in water contain two molecules of water of crystalliza- 
tion, which they lose at 100°. The dry crystals melt at 220°. 

TOLUOL AND ITS DERIVATIVES. 

Toluol is a homologue of benzol. It was discovered in 1837 
by Pelletier and Walter; H. Deville has obtained it by distil- 
ling balsam of Tolu ; hence its name. It exists in coal-tar, 
and may be separated from that body, like benzol by fractional 
distillation. Its density at 0° is 0.882. It boils at 111°. It 
is luetliijl-phcuijj, or iiu'tht/l henzol, and has been oljtained by 
synthesis by heating a mixture of methyl iodide and monobro- 
mobenzol with sodium (Fittig and Tollens). 

en^Br + CH'I + 2Na .= Nal + NaBr -f C^H^-CIF 

Monobroniobenzol. Methyl-plionyl. 



TOLUOC*. G19 

A method of synthesis of tohiol, wliicli by the generality of 
its appHeations is one of the most fecund in chemistry, is due 
to Friedel and Crafts. It consists in the reaction of methyl 
chloride on benzol in presence of aluminium chloride. Toluol is 
formed, and hydrochloric acid is disengaged. It is probable that 
the aluminium chloride first acts on the benzol, disengaging 
hydrochloric acid and forming a phenyl derivative of aluminium 
chloride, which derivative is continually formed and continually 
decomposed by the methyl chloride. The cycle of reactions 
would then be represented by the following two equations : 

cm' + APCP = APCP(C'H^) -f HCl 
APCPCC^H^) + CH^Cl = C«H\CH3) + APCP 

We may add that the toluol thus formed may react with an 
excess of methyl chloride, forming hydrochloric acid and dime- 
thyl benzol (xylol), which in its turn may react upon an excess 
of methyl chloride. It is thus seen that the methylation of 
benzol does not stop with the first substitution compound, and 
that the nature of the products formed depends upon the pro- 
portions of the bodies which react. Friedel and Crafts have 
thus succeeded in introducing six methyl groups into benzol, 
and have made the synthesis of hexamethylbenzol. 
C'R' + eCffCl = 6HC1 + C*'(Cff)« 

Hexametliylbenzol. 

When toluol is boiled with dilute nitric acid, or with a solu- 
tion of chromic acid, it is transformed into benzoic acid. 

Substitution Products of Toluol. — These compounds are 
numerous, and present various isomerisms, of which we will 
consider the principles. 

When chlorine acts upon toluol, I , one or more atoms 
^ ' CW ' 

of hydrogen may be removed and replaced by as many atoms 

of chlorine. The most simple of the products thus formed is 

the compound C^H^Cl, which results from the substitution of 

one atom of chlorine for one atom of hydrogen in toluol, C^H®. 

But this substitution may take place in the benzol nucleus 

C^ff, or in the lateral chain CH^, and two isomeric bodies are 

thus formed, monochlorotoluol and benzyl chloride. 

C6H1C1 C6H5 

CH3 CH2C1 

Monochlorotoluols. Benzyl chloride. 



620 ELEMENTS OF MODERN CHEMISTRY. 

Monochlorotoluol, C^H*<p, , is a di-substituted derivative 

of benzol ; it may consequently exist in three isomeric modifi- 
cations, as has already been explained (page 59-4). 

It is thus seen that there are four difierent bodies derived 
from toluol by the substitution of one atom of chlorine for one 
of hydrogen, namely, benzyl chloride and three monochloro- 
toluols. 

The followino; table includes a number of toluol derivatives : 



C6H1C1 


C6II*(NH2) 


C6H^(0H) 




C6H*(0H) CHl\OK) 


Monochlo- 
rotoluol. 

C6H5 


CH3 
Toluidine. 

C6H5 


CH3 

Cresol. 

C6H5 


C6H5 


CHO CO.OH 
Salicyl Salicylic acid, 
hydride. 

C6H» 


CH2C1 
Benzyl 
chloride. 


CH2(NH2) 

Benzyla- 

mine. 


CH2.0H 
Benzyl 
alcohol. 


CHO 
Benzyl 
aldehyde. 


CO.OH 
Benzoic acid. 



Among these compounds, those placed in the same vertical 
line present isomerisms easily understood from the formulae, 
which express their constitutions and show the atomic group- 
ings. 

Those bodies in the first horizontal series constitute di-sub- 
stituted compounds of benzol. 

C«H<CH3^ C6H4<CH^ CBH^gHO C6H^<^^^0H 

Toluidines. Cresols. Salicyl hydride. Salicylic acid. 

Hence they may exist in three different isomeric modifica- 
tions, and consequently there are four isomerides of each of 
these derivatives of toluol, excepting salicylic acid, just as for 
monochlorotoluol. 

Chloro-Derivatives of Toluol. — Benzyl chloride, C^IP- 
CH"C1, is formed when chlorine is passed into boiling toluol. 
It is a colorless liquid, having an irritating odor, and boiling 
at 17G°. 

The monoclilorotoluols are formed by the action of chlorine 
on cold toluol. Ortho- and metachlorotoluol are liquids, boil- 
ing between 156 and 157° Parachlorotoluol boils at 160.5°, 
and below 0° solidifies to a mass which melts at 6.5°. 

Nitrotoluols. — Monohydrated nitric acid attacks toluol and 
converts it into nitrotoluol, C^H^(NO0, and dinitrotoluols, 
according to the duration of the reaction. There are three 

nitrotoluols, C''H*<^0-^ 



CRESOLS — OllCIN. 621 

Ortlionitrotoluol, a yellow liquid, boiling between 222 and 
223°. 

Metanitrotoluol, crystals, fusible at 1(5°. Boils at 230-231°. 

Paranitrotoluol, almost colorless prisms, fusible at 54°, and 
boilinu- at 236°. 

Dinitrotoluol, Q^^^OyQW, is formed when toluol is 
treated with a mixture of nitric and sulphuric acids. Long 
needles, almost colorless, fusible at 'ZO.S". An isomeride is 
known, fusible at 60°. 

CKESOLS. 

There are three cresols, two solid and one liquid. They 
may be formed artificially by treating toluol with sulphuric acid, 
according to the process indicated on page 600 ; but in this 
reaction several isomeric sulphoconjugated acids are formed, 
and when decomposed by potassium hydrate, they yield differ- 
ent cresols. 

The liquid cresol discovered by Fairlie, and extracted from 
wood-tar by Duclos, is a colorless liquid, having an odor like 
that of phenol. It boils at 189-190°. It appears to be a 
mixture. 

Orthocresol is a crystalline mass, fusible at 31°, and boiling 
at 185-186°. 

Metacresol is liquid. 

Paracresol forms colorless prisms, fusible at 34.5°. It boils 
at 201° (A. Wurtz). 

ORCIN. 

C7H802 

This body is an oxycresol. It was discovered by Robiquet 
in 1829, and is obtained, at the same time as erythrite, by 
decomposing erythrin by slaked lime at 150°. 

The orcin is deposited first in beautiful crystals from the 
solution which contains both substances, and it is purified by 
recrystallization. It forms colorless, hexagonal prisms, con- 
taining one molecule of water of crystallization. It melts at 
58°, losing its water, and the anhydrous orcin boils at 290°. 

The crystals of orcin become rose-colored in the air. When 
ammonia is added to their aqueous solution and the liquid is 



622 ELEMENTS OF MODERN CIIEMISTRV. 

exposed to the air, it absorbs oxygen and assumes first a violet 
color and afterwards a brown. A nitrogenized body is formed 
which is known as orcein^ and constitutes the coloring principle 
of the orchil of commerce. 

The synthesis of orcin has been made by the action of fused 
potassium hydrate on the sulphoconjugatcd acid of mono- 
chlorotoluol (crcsyl chloride, C^H'Cl.CH'^). The chlorine and 
the group, SO'H, of this compound are thus replaced by two 
groups OH (Vogt and Henninger). 

rci roH , 

C6H3^S03K + 2K0H = S03K2 + KCl + Cm^lOR 

{ CH3 ( CH3 

Potassium chlorocresyl- Orcin. 

sulphite. 

TOLUIDINES. 

C7H9N = C6U4(NI12)-CH3 

Paratolmdine. — Solid toluidine, which is paratoluidine, was 
discovered by Hofmann and Muspratt in 1848. They obtained 
it by the reduction of paranitrotoluol by ammonium sulphy- 
drate. This reduction may also be accomplished by iron and 
acetic acid, or by tin and hydrochloric acid. 

C^H^(NO^) + 3H^ == C"H^(NHO + 2ffO 

Nitrotoliiol. Toluidine. 

An interesting method of formation of paratoluidine was dis- 
covered by Hofmann and Martins. When methylaniline hydro- 
chloride is heated to 350° under pressure, paratoluidine hydro- 
chloride is formed. The methyl group which is united to the 
nitrogen of the former base is then transposed and exchanged 
for an atom of hydrogen of the phenyl group. 

^CHV> ^C6H4-CH3 

N^CH3 N^H 

II H 

Methylaniline. Toluidine. 

Paratoluidine is a solid heavier than water. It crystallizes 
from its dilute alcoholic solution in large plates. It melts at 
45°, and boils at 198°. It is almost insoluble in water, but 
very soluble in alcohol and in ether. 

Toluidine exists nearly always in commercial aniline. It is 
important and necessary for the i)reparatioii of certain aniline 
colors. 

Orthotoluidine was discovered by Rosenstiehl in commercial 



BENZYL ALCOHOL. 623 

toluidine, which is a mixture of para- and orthotoluidine. It is 
formed by the reduction of ortlionitrotokiol by nascent liy- 
droiien. It is liquid and does not solidify at — 20°. It boils 
at ii)J).5°. 

Mctatoluidine — A colorless liquid, boiling at 197°. Density 
at 25°, 0.998. 

BENZYL ALCOHOL. 

C^H^O = C6115_CH2.0H 

Cannizzaro obtained this body by heating oil of bitter 
almonds with an alcoholic solution of potassium hydrate. 

2C^IF0 + KOH =:= KC^H^O^ -f- C^H«0 

Beuzyl aldehyde. rotiissium benzoate. Benzyl alcuhol. 

Toluol may be converted into benzyl alcohol. It is boiled 
in a current of chlorine, and benzyl chloride is thus formed, 
C'H'Cl.* This chloride may be transformed into benzyl 
alcohol by heating it with potassium acetate and decomposing 
the benzyl acetate so formed by potassa. 

C-H^Cl H- KC'^H^O^ = C^irOlC^H^ + KCl 

Benzyl chloride. Benzyl acetate. 

Qm\C'WO\ -\- KOH = KC^H^O^ + C^H^OH 

Benzyl acetate. Benzyl alcohol. 

Benzyl alcohol, or benzyl hydrate, is a colorless, oily liquid, 
having a faint but agreeable odor. It boils at 207°. Density 
at 0°, 1.0628. 

When heated with nitric acid, it is converted into benzyl 
aldehyde (oil of bitter almonds). 

C^H«0 + =. H^O -h C^IPO 

Chromic acid oxidizes it to benzoic acid. 

C^H«0 + 0^ = H^O + C'H«0' 

The relations between benzyl alcohol, benzyl aldehyde, and 
benzoic acid are the same as those between alcohol, aldehyde, 
and acetic acid. 

CH3-CII2.0H alcohol. CGH5-CH2.0H benzyl alcohol. 

CH3-CH0 aldehyde. C6H5-CHO benzyl aldehyde. 

CII'^-C02n acetic acid. QHl^-COni benzoic acid. 

*- When chlorine is passed into cold toluol, benzyl chloride is not formed, 
but monochlorotoluol (page 620). 



G24 ELEMENTS OF MODERN CHEMISTRY. 

Benzyl Compounds. — Benzyl ddoride^ C^H^Cl = C^H^- 
CH^Cl, is formed, as has already been remarked, when chlorine 
is passed into boiling toluol. It is also formed by the action 
of hydrochloric acid on benzyl alcohol by the aid of heat. It 
is a colorless liquid having an irritating odor. It boils at 
176°. 

Benzylamine, C^H^-CH'.NHl— This body is formed by the 
action of nascent hydrogen on benzonitrile (phenyl cyanide), 
which thus fixes four atoms of hydrogen. It is also formed 
in small quantity, together with dibenzylamine and tribenzyl- 
amine, when benzyl chloride is heated with alcoholic ammonia. 
It is a limpid liquid, boiling at 185°, and miscible with water, 
alcohol, and ether. Density, 0.99 at 14°. 

Trihenzylamine, (C^H^.CH^)'N. — This is formed in abun- 
dance by the action of a hot alcoholic solution of ammonia on 
benzjd chloride. It cr3^stallizes in beautiful, colorless needles 
or plates, fusible at 91°. It is insoluble in water, slightly 
soluble in cold alcohol, very soluble in hot alcohol and in ether. 



BENZYL ALDEHYDE. 

C^HeO = C6H5-CHO 

This body, also called benzoyl hydride, exists in the essential 
oil of bitter almonds, mixed with hydrocyanic acid, both sub- 
stances being formed by the action of emulsin and water on 
amygdalin (page 587). 

Benzyl aldehyde is a colorless, strongly-refracting liquid, hav- 
ing a pleasant odor and a pungent, aromatic taste. It boils at 
179.5°. 

When its vapor is passed through a porcelain tube filled with 
pumice-stone and heated to redness, benzyl aldehyde breaks up 
into benzol and carbon monoxide. 

C'lPO = CO -f Q'W 

When exposed to air and light, it absorbs oxygen, and is con- 
verted into benzoic acid. 

C^IPO 4-0 = C'H^O^ 

Benzoic acid. 

Nascent hydrogen, produced by the action of water on 



BENZOYL CHLORIDE. 625 

sodium amalgam, transforms benzyl aldehyde into benzyl alco- 
hol (Friedel). 

C^H^O + ff = C'H^OH. 

Chlorine and bromine convert it into chloride and bromide 
of benzoyl ; hence the name benzoyl hydride. 

C^H^O.H + CP = HCl + C^ffO.Cl 

Benzyl aldehyde. Beuzuyl chloride. 

When crude oil of bitter almonds containing hydrocyanic 
acid is mixed with alcoholic potassium hydrate, or when the 
pure oil is mixed with an alcoholic solution of potassium cya- 
nide, the benzyl aldehyde is polymerized and converted into a 
solid body, which is hoizom, C^^H^'-'O'^ The latter body crystal- 
lizes in brilliant, colorless prisms, fusible at 133-134:°. It is 
but slightly soluble in water and cold alcohol, very soluble in 
boiling alcohol. 

Benzoyl Chloride, C^H^-COCl.— This body is also formed 
by the action of phosphorus pentachloride on benzoic acid or a 
dry benzoate. It is a colorless, highly-refractive liquid, having 
a peculiar, irritating odor. It boils at 190°. Water decom- 
poses it into benzoic and hydrochloric acids. 

C^H^O.Cl + H^O = CTPO.OH + HCl 

Ammonia converts it into benzamide. 

C^mOCl + NH^ = C^H^O.NH^ + HCl 

Beiizuniide. 

Benzoyl chloride may exchange its chlorine for other ele- 
ments. When it is distilled with potassium iodide, potassium 
chloride and benzoyl iodide are formed. Liebig and Wohler, 
who discovered these important reactions, prepared in the 
same manner, by double decomposition, benzoyl sulphide and 
benzoyl cyanide. These experiments are celebrated ; they 
were the starting-point of the benzoyl theory^ which marked 
an important progress in the development of the theory of 
radicals. The following formulae indicate the principal benzoyl 
combinations : 

C^H^O.H benzoyl hydnrle (oil of bitter almonds). 

CTH^O.Cl benzoyl chloride. 

C'H^O.I benzoyl iodide. 

(Cni50)2S benzoyl sulphide. 

C'^H^O.OH benzoyl hydrate (benzoic acid). 

Cm50.NH2 benzamide. 

2b 63 



62G 



ELEMENTS OP MODERN CHEMISTRY. 



BENZOIC ACID. 

^7H602 = C6H5-C02H 

Preparation. — This acid may be obtained from gum benzoin. 
That re.siu is phiced in a flat dish over the top of which a sheet 
of tissue-paper, or light fiUer-paper is glued (Fig. 131). This 
diaphragm forms the base of a paper cone which is then placed 
over the dish, which is moderately heated on a sand-bath for 

several hours. At the 
end of that time, the 
whole is allowed to 
cool, and the benzoic 
acid is found in light, 
brilliant, crystalline 
flakes on the sides of 
the cone, and on the 
diaphragm. 

The benzoin resin 
may also be powdered 
and digested with milk 
of lime for twenty- 
four hours ; it is then 
heated to ebullition 
and filtered. Hydro- 
chloric acid precipi- 
tates benzoic acid from the filtered liquid, which contains cal- 
cium benzoate. 

In Germany, large quantities of benzoic acid are prepared 
by boiling the urine of horses and cows with hj^drochloric acid. 
The hippuric acid which these urines contain is thus decom- 
posed into benzoic acid and glycocol. The benzoic acid crys- 
tallizes on cooling, and is purified by sublimation. 

Properties. — Benzoic acid crystallizes in needles, or in thin, 
brilliant plates. It has an aromatic odor, and a slightly acid 
taste. It melts at 121°, and boils at 250°. 

It dissolves in 607 parts of water at 0°, and in about 12 
parts of boiling water. AVhen boiled with a quantity of water 
insufiicient to dissolve it, it melts. It volatilizes with the vapor 
of water. It dissolves readily in alcohol and in ether. When its 
vapor is passed over red-hot pumice-stone, contained in a porce- 
lain tube, it is decomposed into carbonic anhydride and benzol. 




Fig. 131. 



HIPPURIC ACID. G27 

When heated with phosphorus pcntachloride, it yields ben- 
zoyl chloride. 

C^tPO.OII + PCP = POCP + HCl + C^IPO.Cl 

Benzamide, C'H^-CO.NHl— This body is formed by the 
action of ammonia gas on benzoyl chloride. 

C^H^CO.Cl + 2NH^ = NH*C1 + C^IP-CO.NH^ 

It is also formed by the action of ammonia on ethyl benzoate. 

C«H^-CO.OCTP -f NH^ = en^OH + C^IP-CO.NH'^ 

Ethyl benzoate. Alcohol. Benzamide, 

It occurs in brilliant, colorless, oblique rhombic crystals, 
fusible at 128°, and can be sublimed without decomposition. 
It is soluble in hot water and in alcohol. 

Benzoic Acetone, Benzophenone, or Diphenyl-ketone, 
C13JJ10Q ^ CTL^-CO-C'H^— This body is formed, to-ether 
with benzol, in the destructive distillation of calcium benzoate 
(Chancel). 

Ca(eH^-CO0' = CaCO^ + (C''H^)^CO 

Calcium benzoate. Diphcnyl-ketonc. 

It forms large, colorless, or slightly yellow, right rhombic 
prisms, fusible at 48-49°, and boils at 295°. It is insoluble 
in water, but very soluble in alcohol. 

Friedel and Crafts obtained it by treating benzol with chloro- 
carbonic gas in presence of aluminium chloride. 

2C*^H« + COCP = 2HC1 + (C'lP/CO 

HIPPURIC ACID. 

CO.OH 

One of the most important of the benzoic derivatives is hip- 
puric acid. Its relations with the benzoic scries are manifested 
by its decomposition by hydrochloric acid into benzoic acid and 
glycocol. 

C^H^NO^ + H^O = C^H^NO^ -\- C^H^O' 

Hippuric acid. Glycocol. Benzoic acid. 

Rouellc, Fourcroy, and Vauciuelin discovered this acid in 
the urine of the horse, but confounded it with benzoic acid. 



G28 ELEMENTS OF MODERN CHEMISTRY. 

Its true nature was recognized by Liebig in 1830. Dossaignes 
has made its synthesis by the reaction of benzoyl chloride on 
the zinc compound of glycocol. 

CfH^NO^ + C^H^O.Cl = C'H*(C^H^O)NO^ + HCl 

Glycocol. Benzoyl chloride. Hippiiric acid. 

Hippuric acid is obtained from the urine of horses and cows 
by mixing the urine with 2 or 3 times its volume of concen- 
trated hydrochloric acid. The hippuric acid separates in col- 
ored crystals. 

When properly purified, it crystallizes in long, colorless 
prisms, but slightly soluble in cold water, very soluble in boil- 
ing water and in alcohol. When heated in a retort, it decom- 
poses and yields a sublimate of benzoic acid. At the same 
time a certain quantity of an oily body having a disagTeeable 
odor distils: it is phenyl cyanide, or benzonitrile, CN.C^H^ 



SALICYL ALDEHYDE, OR SALICYL HYDRIDE. 

C'H602 = C«H4(0H).CH0 

This compound, which is isomeric with benzoic acid, exists 
naturally in the essential oil of the meadow-sweet (Spirsea vl- 
inaria). Piria obtained it by oxidizing salicin by potassium 
dichromate and sulphuric acid (page 588). 

It is a colorless, highly refracting liquid, and boils at 196.5°. 
Its density at 13.5° is 1.173. Its odor is pleasant and its 
taste burning. It is quite soluble in water, and dissolves in 
alcohol and ether in all proportions. It has an acid reaction. 
It produces a violet color with ferric chloride. Oxidizing 
agents convert it into salicylic acid. 

C^H^O' -f O = C^H«0' 

By the action of fused potassium hydrate, it is likewise 
transformed into salicylic acid, with disengagement of hydrogen. 

C^H^O^ -{- KOII = KC^H^O^ + H^ 

Salicyl aldehyde. Potassium salicylate. 

In presence of sodium amalgam and water, it fixes H^ and 
is converted into saUgeniii (Reincke and Beilstein). 

Q'wo' -\- w = (j'W(y 

Salicyl aldehyde. Saligenin. 



SALICYLIC ACID. 629 

The latter body is also formed, according to Piria, by the 
decomposition of salicin by ferments and acids (page 588). It 
crystallizes in tables having a pearly lustre, or in small, brilliant 
needles. 

SALICYLIC ACID. 

CTH603 = C6H*(OH).C02H 

Formation and Preparation. — This body was discovered 
by Piria, who obtained it, in 1839, by fusing salicyl aldehyde 
with potassium hydrate. 

C^H^O^ + KOH = KC^IPO^ + W 

Oil of meadow-sweet contains it naturally, together with 
salicyl aldehyde. The essential oil of Gaultheria j^i'ocumhens 
(winter-green) is methyl salicylate (Cahours), that is, sali- 
cylic acid, in which the atom of basic hydrogen is replaced by 
methyl. 

Salicylic acid is ordinarily prepared by boiling oil of winter- 
green with caustic potassa as long as methyl alcohol is dis- 
engaged. Potassium salicylate is formed, and is afterwards 
decomposed by an excess of hydrochloric acid. The salicylic 
acid separates, and is purified by recrystallization from boiling 
water. 

Kolbe and Lautemann formed salicylic acid by synthesis by 
passing carbon dioxide into phenol in which sodium was dis- 
solved. Sodium salicylate is thus formed. 

C«H^OH + CO.O = C*^H*(OH) 

CO.OH 

PhenoL Salicylic acid. 

Kolbe has recently improved this process. Indeed, salicylic 
acid is formed by simply passing dry carbon dioxide over 
sodium phenate at a temperature of 180°. The temperature 
is finally raised to 250°, and the product of the reaction, freed 
from an excess of phenol by distillation, constitutes sodium- 
salicylate of sodium. 

2C«H5.0Na + CO^ = C«H10H + C^H* I ^^^^ 

Sodium phenate. Phenol. Sodium-salicylate of sodium. 

The mass is exhausted with water, and the solution is treated 
with hydrochloric acid, which sets free the salicylic acid. 

53* 



630 ELEMENTS OF MODERN CHEMISTRY. 

Tins process permits of the rapid and economical manu- 
facture of large quantities of salicylic acid. 

Properties. — Salicylic acid crystallizes from its alcoholic 
solution in large, quadrilateral prisms, and from its aqueous 
solution in long needles. It melts at 156°. When mixed with 
pumice-stone and rapidly distilled, it breaks up into carbon 
dioxide and phenol. 

It is very soluble in alcohol and ether, and in boiling water, 
but cold water scarcely dissolves it. Its aqueous solution pro- 
duces a deep violet color with the ferric salts. 

When salicylic acid is treated with nitric acid, it is converted 
into two isomeric nitrogenized acids ; both are nitrosalicylic 
adds, C^H=(NO'0Ol 

a-nitrosalicylic acid crystallizes in long, colorless needles, 
which are anhydrous and melt at 228° ; they are very slightly 
soluble in cold water. It produces a blood-red color with ferric 
chloride. 

/5-nitrosalicylic acid crystallizes in long, colorless needles, 
containing one molecule of water of crystallization. When 
heated, it loses this water and melts at 144-145°. It is slightly 
soluble in cold water. Its solution also produces a blood-red 
color with ferric chloride. This acid is also formed when 
indigo is long boiled with nitric acid. It was formerly called 
indigotic acid. 

Salicylic acid possesses antiseptic properties like phenol, 
without presenting the same inconveniences as the latter as 
regards odor and causticity. 

Methyl Salicylate, C'H^CHOOl— Cahours first recognized 
the oil of Gaulthen'a, known as essence of winter-green, to be 
methyl salicylate. When purified, this body forms a colorless 
oil, having a pleasant odor. It boils at 223.7°. Its density at 
0° is 1.1969. Like the phenols, it has the characters of a 
weak acid. When a concentrated solution of potassium hy- 
drate is added to methyl salicylate, a precipitate of potassium 
gaultherate is formed. Cahours discovered the existence of an 
isomeride of methyl salicylate. It is mcthylsalicylic acid. The 
following formulae indicate the constitutions of these bodies : 

C6IR0H CfilROII C6H*.0K C6H*.0CH3 C^H^.OCIl^ 

CO.OIi C0.0CH3 C0.0CH3 CO.OH C0.0CII3 

Salicylic acid. Methyl Potassium MethvLsiilicylic Methyl 

salicylate. gaultherate acid. methylsalicylate. 



OXYBENZOIC AND PAROXYBENZOIC ACIDS. G31 



OXYBENZOIC AND PAROXYBENZOIC ACIDS. 

These two acids are isomeric with salicylic acid. 

Oxybenzoic Acid is formed under various circumstances ; 
especially when metachloro-benzoic acid, a chloro-derivative 
of benzoic acid, is heated with potassium hydrate. 

C^ffClO^ + 2K0H = C^HXOK)0^ + KCl + H^O 

It is an anhydrous, crystalline powder, consisting of small, 
square tables. Sometimes it is in mammillated crystals. It melts 
at 200°, and can be distilled without alteration. It is only 
slightly soluble in cold water, but dissolves more readily in boil- 
ing water. 

Paroxybenzoic Acid is formed under rather remarkable cir- 
cumstances. We have already seen that in presence of sodium, 
phenol fixes carbon dioxide, forming sodium salicylate. If the so- 
dium be replaced by potassium, the same reaction produces potas- 
sium paroxybenzoate. The same salt is formed when potassium 
phenate is heated to 210 or 220° in a current of carbon dioxide. 

Paroxybenzoic acid crystallizes in transparent, oblique rhom- 
bic prisms, containing one molecule of water of crystallization. 
When anhydrous, it melts at 110°. It is much more soluble 
in water and alcohol than salicylic acid. Its aqueous solution 
does not produce a violet color with ferric chloride. 

Anisic Compounds. — When the oils of anise, of fennel, or 
of tarragon are heated with nitric acid, they are converted into 
a colorless oil, having a spicy odor, and boiling at 248°. This 
is anisic aldehyde^ C^H^O^. By a more complete oxidation, 
this aldehyde is converted in anisic acid, C^H^O\ Anisic alde- 
hyde and acid present very simple relations of composition with 
paroxybenzoic acid. 

Anisic aldehyde is metliylparoxyhenzoic aldehyde, and anisic 
acid is methylpar oxybenzoic acid. 

C»«'<CO.OH CeH*<0<jH'j, '^^i^<lZ' 

Paroxybenzoic acid. Methjiparoxybenzoic, Methylparoxybenzoic, 

or anisic acid, or anisic aldehyde. 

TYROSINE. 

C9H11N03 

This body seems to be related to the preceding compounds. 
It may be regarded as amidopropionic acid in which one atom 



632 ELEMENTS OF MODERN CHEMISTRY. 

of hydrogen is replaced by the group C^H*.OH (paroxyphenyl) 

as it exists in paroxybenzoic acid. 

C2H5 C2H*(NH2) C2Ha(C6H*.OH)(NH2) 

com C02H C02H 

Propionic acid. Amidopropionic acid. Oxyphenyl-amidopropionic 

acid (tyrosine). 

Tyrosine is the product of the decomposition of many nitro- 
genized matters in the animal economy. It may be prepared 
by boiling for sixteen hours 1 part of horn shavings with 2 
parts of sulphuric acid diluted with -i times its volume of water. 
The liquid is then neutralized with milk of lime, filtered, the 
filtrate evaporated to half its volume, acidified with sulphuric 
acid, and treated with an excess of lead carbonate. 

The solution, which contains the tyrosine as lead salt, is de- 
composed by hydrogen sulphide, filtered, and evaporated. The 
tyrosine crystallizes out, and may be purified by several crystal- 
lizations. The mother-liquors contain leucine. 

Tyrosine crystallizes in long, colorless needles, often united 
in tufts. It is but slightly soluble in water and in cold alcohol, 
more soluble in hot alcohol, and insoluble in ether. It forms 
definite compounds with both acids and bases. When fused 
with potassium hydrate, it breaks up into paroxybenzoic and 
acetic acids, and ammonia. 

Tyrosine may be recognized by the following reaction. 
When its aqueous solution is boiled with a solution of mer- 
curic nitrate, as neutral as possible, a voluminous yellow precip- 
itate is formed, which assumes a deep copper-red color by 
boiling with nitric acid containing a small quantity of nitrous 
acid. 

GALLIC ACID. 

C7H605 == C6H2(OH)3 - CO.OH 

This acid is closely related to salicylic acid. It is dioxysali- 
cylic acid, and Lautemann obtained it by treating di-iodosali- 
cylic acid with alkalies. 

C^HTO' + 2K0H = 2KI + C^H^(0H)20' 

Di-iodosalicylic acid. Gallic acid. 

We have already seen that gallic acid is a product of the 
decomposition of tannic acid. It is prepared by exposing 
coarsely-powdered and moistened nut-galls to the air, renewing 
the water as it evaporates. At the end of two or three months 



INDIGO. 633 

a black liquid is separated from the mass by stronii; pressure, 
and the solid residue is exhausted with boilin<;- water. Gallic 
acid crystallizes out on the cooling- of the filtered liquid. It is 
puritied by several crystallizations in boiling water. 

Gallic acid forms long, silky needles, which contain one 
molecule of water of crystallization. It has no odor ; its taste 
is astringent and slightly acid. When heated to 100°, it lo.ses 
carbon dioxide and is converted into a body which sublimes 
in brilliant white laminae. This is pyrogallol, or pyrogallic 
acid, and is employed in photography. 

Gallic acid. ryrogallul. 

Gallic acid dissolves in 100 parts of cold water, and in 3 
parts of boiling water. It is very soluble in alcohol, less soluble 
in ether. Its solution gradually absorbs oxygen when exposed 
to the air, and at the same time becomes colored and disengages 
carbon dioxide. 

If a recently boiled solution of gallic acid be passed up into 
a tube filled with mercury and containing no air, and some 
recently boiled baryta-water be then added, a white precipitate 
is formed which at once changes to blue, if a few^ bubbles of 
oxygen be introduced. The change of color is the indication 
of an oxidation of the gallic acid, favored in this case by the 
presence of the alkali. 

INDIGO. 

C8H5NO 

Indigo is obtained from difierent species of the genus Indi- 
gofera. The pastel, or woad (Imtis tinctoria), also furnishes a 
coloring matter identical with indigo. 

In India, indigo is prepared by macerating the stems and 
leaves of the indigofera, collected at the time of flow^ering, with 
w^ater, in vats where they are allowed to ferment. In 12 or 
15 hours the liquid is drawn off into other vats, where it is 
agitated so as to bring it in contact wath the air, an opera- 
tion which occasions the formation of a blue precipitate. The 
brown liquor is then drawn off, and the deposit is boiled in 
copper vessels ; it is then pressed between cloths and cut into 
cubical pieces and dried. In this form the indigo is delivered 
to commerce. 

Indigo is not contained ready formed in the plants whicli 
2b- 



634 ELEMENTS OF MODERN CHEMISTRY. 

serve for its manufacture. Scliunck lias shown that these phints 
contain a substance analogous to the glucosides, imlican, which 
is decomposed by fermentation into indigo and iiidoglucin. 

IiidiciUi. Indigo. Indoglucin. 

Indican has been found in human urine. 

The indigo of commerce contains from 50 to 90 per cent, of 
coloring matter. It generally occurs in irregular masses, some- 
times cubical, of which the shade varies from violet-blue to 
blackish-blue. The most esteemed varieties present a brilliant 
coppery reflection. 

Pure indigo is called indigotine. It may be obtained by 
heating the indigo of commerce in a current of hydrogen, or 
by subliming it in small quantities between two watch-glasses 
(Chevreul). It then forms right rhombic prisms having four 
or six faces. Indigotine is insoluble in water, in cold alcohol, 
and in ether. Boiling alcohol and oil of turpentine dissolve it 
to a slight extent. 

Concentrated, or better, fuming sulphuric acid dissolves in- 
digo at 50 or 60°, forming a beautifid blue solution, which 
contains two acids, sulphimUgotic acid, C^H^NO.SO'^H, and 
sidphopuvpuric acid, C^'^H^N'-^O'^SO'^H. The solution of indigo 
in sulphuric acid is used in dyeing ; it is prepared by dissolving 
indigo in a hot mixture of fuming and ordinary sulphuric acids. 
The blue solution thus obtained is known as sulphate of indigo, 
Saxon blue, or composition blue. 

Boiling dilute nitric acid converts indigo into isatin. The 
concentrated acid converts it first into nitrosalicylic acid, C'H^ 
(NO-jO*, and then into picric acid. 

When heated with potassium hydrate, indigo is converted 
into anthranilic acid, C^H^(NH''^)0'^, or into salicylic acid, 
which is formed at the expense of the anthranilic acid. 

C^IP(Nir^)0^ + KOH = KC^H^O^ + NH^ 

Authranilic acid. Potassium salicylate. 

When indigo is distilled with potassium hydrate, aniline 
passes over, being formed at the expense of the anthranilic acid 
first formed. 

C^IFNO^ = CO' + C^H^N 

Anthranilic acid. Aniline. 

White Indigo, C^IP'^N'O'.— This body, which was discov- 
ered by Chevreul in 1812, results from the action of nascent 



ISATIN. 635 

hydrogen on indi^'O. It is produced wlien the latter substance 
is submitted to the action ot* alkaHne sohitions in presence of 
reducing matters, such as sulphurous or phos})h{)rous acid, 
hydrogen sulphide, iron, zinc, or ferrous or stannous hydrate. 
2C«H^N0 + W = C'^H^^N^O^ 

White indigo is ordinarily prepared by introducing a mix- 
ture of indigo, ferrous sulphate, slaked lime, and water into a 
vessel, which should be entirely filled with the mixture and 
then hermetically sealed and allowed to stand for two days. A 
clear, alkaline solution is thus obtained, which is decanted, and 
supersaturated with hydrochloric acid, out of contact with the 
air. A deposit of white indigo is formed, and must be collected 
on a filter, rapidly washed with boiled water, and dried in a 
vacuum. 

The body thus obtained has a dirty-white color, and is with- 
out either taste or smell. It is insoluble in water, but dissolves 
with a yellow color in alcohol, ether, and alkaline solutions. 
On contact with air it absorbs oxygen, and is converted into 
blue indigo. Nitric acid rapidly brings about this transformation. 

Uses. — Indigo is largely used in dyeing. The principle of 
its application depends on the conversion of the blue indigo into 
white indigo by reducing agents. The reduced white indigo 
is soluble in alkaline solutions and in this form is fixed on the 
fabrics, after which it is reconverted into blue indigo by ex- 
posure to the air. The mixture just indicated for the prepara- 
tion of white indigo (ferrous sulphate, indigo, lime, and water) 
is most frequently employed. It constitutes what is known as 
the vitriol vat. 

Schiitzenberger and de Lalande have recently described a 
process of dyeing with indigo, based on the employment of 
sodium hydrosulphite. 

ISATIN. 

C8H5N02 

This body was discovered by Erdmann and Laurent in 1841. 
It is a product of the oxidation of indigo by dilute nitric acid. 
C«H^NO + = C^H^NO' 

Pure isatin crystallizes sometimes in large, dark, gold- 
colored prisms, sometimes in small, reddish-yellow prisms 
having a brilliant lustre. It is only slightly soluble in cold 
water and in ether, but more soluble in boiling water, and very 



636 ELEMENTS OF MODERN CHEMISTRY. 

soluble in alcohol. When distilled with potassa, it yields 
aniline. 
C^PNO^ H- 4K0II =: 2K'C0' -h C«H"N -[- H^ 

lisatiii. Aniline. 

By the action of chlorine, isatin yields substitution pro- 
ducts. These latter break up, like isatin itself, by the action 
of potassium hydrate, yielding cJiIoranilines (Hofniann). 

C^H^CINO^ -I- 4K0H .^^ 2K'C0' + CWCm -f H^ 

Monoclilorisatin. Monochloriuiilino. 

Products of the Reduction of Isatin. — To isatin are re- 
lated certain products of its reduction, which are interesting 
and which have been studied b}' Knop and Baeyer. They are 

Dioxindol C8irN02 
Oxindol C^IITNO 
Indol C^IFN 

The first two are formed successively by the action of sodium 
amalgam on an aqueous solution of isatin. 

C^H^NO' + H' = eH'NO' 

Isatin. Dioxinflol. 

C«H^NO^ -f- H^ = C^H'NO + H^O 

Dioxindol. Oxindol. • 

By reducing oxindol by zinc powder with the aid of heat, 
Baeyer obtained indol. 

C^tFNO + Zn = C^^H'N + ZnO 

Oxindol. Indol. 

Indol is a crystallizable solid, fusible at 52°. It volatilizes 
with the vapor of water. Its odor recalls that of naphty- 
lamine. It dissolves readily in boiling water, and in alcohol 
and ether. It has basic properties. 

Baeyer has recently obtained isatin and indigo by synthesis. 
By heating phenyl-acetic acid with nitric acid, and reducing 
the nitro-compound so formed, oxindol is obtained. 

This is converted into nitroso-oxindol, ceH^-^^^^^^^l^CO, and 
this by reduction yields ceH^-^^i^^^^l^-CO. By oxidizing the 
latter compound, isatin is obtained, C6II^<^^j>C0. When isa- 
tin is heated with phosphorus pentachloride, hydrochloric acid 
is disengaged, and a chloro-compound is formed, C«JI'*<^ j^^CCl, 

and this by reduction yields indigo, C^ll*<^^^^Cll. 



PHTHALIC ACID. 637 



XYLOLS AND DERIVATIVES. 

That portion of coal-tar which boils between 136 and 139° 
contains a mixture of isomeric hydrocarbons, which is desig- 

nated as xylol or xylene. It is dimethylbenzol, C'^H*<prT:„ 

and can exist in three diiferent isomeric modifications, like all 
of the di-substituted derivatives of benzol. 

Mctaxylol^ which boils at 137°, predominates in the mixture 
of xylols which is obtained from coal-tar. When oxidized by 
chomic acid, it is converted into isophthalic acid, C'^H\CO'"H)^ 

Orthoxi/lol is a colorless liquid, boiling at 1^1:0-1-11°. Nitric 
acid oxidizes it to orthotoluic acid. 

Paraxylol is solid, and crystallizes in oblique rhombic prisms, 
fusible at 15°. It boils at 136-137°. Dilute nitric acid con- 
verts it into paratoluic acid. Chromic acid oxidizes it to ter- 
aphthalic acid. 

There are very man}^ derivatives allied to these isomeric 
xylols. One or more atoms of hydrogen may be replaced, 
either in the benzol nucleus or in the methyl chains, by chlo- 
rine, bromine, or by groups such as OH, NO", NH', etc. The 
methyl chains may be oxidized by boiling the xylols with nitric 
or chromic acid, as indicated above. In this case the group 
CH'* is replaced by the carboxyl group CO. OH, and the hy- 
drocarbons, C'^H*(CH')''^, are converted into either toluic acids 
or phthalic acids, of each of which there are three isomerides. 

^ ^ "^CH^ ^ ^^ \CO.OH ^ ^^ ^CO.OH 

Xylols. Toluic acids. Phthalic acids. 

We cannot describe all of these bodies here, but must limit 
ourselves to a brief description of phthalic acid and its isomer- 
ides. 

PHTHALIC ACID. 
(J8HG0* = C6H^(CO.OH)2 

Ordinary, or Orthophthalic Acid. — Laurent obtained this 
acid by boiling naphthalene for a long time with nitric acid. It 
crystallizes in brilliant scales, or in short, thick prisms, which 
are but slightly soluble in cold water, very soluble in hot water, 
alcohol, and ether. It melts at 21-3°, and loses the elements 
of water at a higher temperature, being converted into phthalic 
anhydride. 

54 



638 ELEMENTS OP MODERN CHEMISTRY. 

C6iii<^,^;j^{| = H20 + C6n^<^.^>o 

riithalic acid. Phthalic anhydride. 

Phtlialic (inhydride crystallizes in long, brilliant prisms, fusi- 
ble at 127-128°. It boils at 277°. It pos.sesses a remarkable 
property, which was discovered by A. Baeyer, and which is now 
applied practically in the arts. AVhen heated with the phenols, 
it combines with them directly with elimination of the elements 
of water, and compounds are obtained which are designated as 
phthaleins. 

Thus, when phthalic anhydride is heated with ordinary 
phenol, two molecules of phenol combine with one molecule 
of phthalic anhydride, with elmnnation of one molecule of 
water, and the phthalein of phenol is obtained. 
c6H4<-co^(3 + t«n5.oii _ 6n4<-co-c6Ji*.on 

^ ^^ ^CO-^^ ^ CfiH5.0II ^ ^^ \C0-C«11^.01I + ^^^ 

Phthalic anhydride. 2 mol. phenol. Phthalein of i.henol. 

When resorcin is heated with phthalic anhydride, two mol- 
ecules of water are eliminated, and a body is obtained to which 
Baeyer has given the uamejiuoresccui. 

^ ^ ^C0-C6H3.0H 

riitlialic anhydride. 2 mol. resorcin. Fluorescein. 

Fluorescein forms orange-red, crystalline grains, insoluble in 
cold water, and but slightly soluble in boiling water. It dis- 
solves readily in solutions of the alkalies and alkaline carbonates. 
Its dilute solutions are yellow, and have a magnificent green 
fluorescence. Hence the name fluorescein. 

Tefrahromo-Jiuoresceui, C'°H®Br^O^, is emploj^ed in dyeing 
under the name eosui. It communicates to silk a beautiful 
rose-red tint. 

Teraphthalic Acid (paraphthalic). — Cailliot obtained this 
body by submitting oil of turpentine to a long ebullition with 
dilute nitric acid. The same acid is formed by the oxidation 
of paraxylol and its derivatives by potassium dichromate and 
sulphuric acid. It is a white powder, almost insoluble in water, 
alcohol, and ether. It sublimes without melting and without 
decomposition. 

Isophthalic Acid (metaphthalic) is formed by the oxidation 
of metaxylol. Long, thin, colorless crystals, slightly soluble in 
water, soluble in alcohol, and fusible above 300°. It may be 
sublimed without decomposition. 



NAPHTHALENE. GoO 



NAPHTHALENE. 

Clone 

This important compound was discovered by Garden in 1820, 
in coal-tar. Its composition was determined by Faraday, and 
its properties and transformations were principally studied by 
Laurent. 

It is a frequent product of the dry distillation of organic 
matters, and is formed in abundance when these matters, or 
the products of their decomposition, are heated to high tem- 
peratures. Thus it is formed in large quantities when tar is 
passed through red-hot tubes. 

Naphthalene is extracted from coal-tar, and is purified by 
crystallization in alcohol, or by sublimation. 

Properties. — Naphthalene occurs in rhombic tables when it 
has been sublimed, and is deposited in prisms from its ethereal 
solution. It melts at 19.2°, and boils at 218°. It is inflam- 
mable, and burns with a very smoky flame. It is insoluble in 
water, slightly soluble in cold alcohol, freely soluble in boiling 
alcohol, and very soluble in ether. 

Nitric acid attacks naphthalene, forming nitro- derivatives, 
among wdiich is nitro-naplitludcne^ C^°H"(NO'^), which crystal- 
lizes in sulphur-yellow, rhombic prisms, fusible at 43°. By 
long boiling with nitric acid, naphthalene is converted into 
phthalic acid, nitrophthalic acid, and oxalic acid. 

Chlorine acts on naphthalene in two ways : it combines di- 
rectly, forming chlorides of naphthalene, and produces numerous 
substitution products which generally combine with an excess 
of chlorine. 

Bromine yields only substitution compounds with naphtha- 
lene. 

Among all these products, we may mention the following : 

Clojisci'i naphthalene dichloride. C^*^IFC1 monochloronaphthalcne. 

Ci0H«C14 naphthalene tetrachloride. C^l^CX^ dichloronaphthalene. 

Cion6C12Cl* dichloronaphthalene tetra- CioiPCia trichloronaphthalene. 

chloride. 

C10C18C12 perchloronaphthalene di- 0^*^01^ perchloronaphthalene. 

chloride. 

Concentrated sulphuric acid dissolves naphthalene, forming 
two acids : 

Naphtylsulphurous acid, CiOH^SO^H 

f SO^H 
Naphtyldisulphurous acid, C^^Il^ j gQsrr 



640 ELEMENTS OF MODERN CHEMISTRY. 

The formation of the first of these acids is expressed in the 
following equation : 

C'W + SO^H^ = WO + C^«H^SO'H 

Naphthaleue. Naplitylsulphurous acid. 

NAPHTOL. 

This body is formed artificially by treating naphthalene with 
sulphuric acid, and fusing the naplitylsulphurous acid so ob- 
tained with potassium hydrate (see page 606). 

C^°H'.S01<: + KOH = K^SO^ + C'W.OR 

rotassiuiii naphtylsulphite. Naphtol. 

It forms silky needles or laminae, soluble in alcohol, ether, 
and benzol, almost insoluble in cold water, slightly soluble in 
boiling water. It melts at 94°. Its aqueous solution produces 
a violet color with chloride of lime. 

An isomeride of naphtol is known, /5-naphtol, fusible at 122°. 

NAPHTYLAMINE. 

C10H9X = C10H7.NH2 

Zinin obtained this base in 1842 by reducing nitronaphtha- 
lene by ammonium sulphydrate, which may be advantageously 
replaced by iron and acetic acid. 

Nitroiiaphtlialene. Naplitylamiiie. 

It forms fine, colorless needles. It sublimes at a gentle heat, 
melts at 50°, and boils without alteration at 300°. It has a 
fetid odor. Its reaction is not alkaline, although it perfectly 
neutralizes the acids, with wdiicli it forms well-defined and 
crystallizable salts. When exposed to the air, the salts of 
naphtylamine acquire a violet color, probably due to an absorp- 
tion of oxygen. 

ANTHRACENE AND PHENANTHRENE. 

CURIO 

Anthracene, which is solid, exists in the less volatile pro- 
ducts of the distillation of coal-tar. It is obtained from the 
last products of this operation. The mass, which has a buttery 
consistence, is squeezed in a filter-press, and the residue is sub- 



ALIZARIN. G41 

mitted to repeated distillations ; it is finally purified by com- 
pression and several crystallizations in benzol. 

Anthracene may be formed artificially by several processes, 
especially by passing the vapor of toluol and various derivatives 
of that body through a tube heated to bright redness. Under 
these conditions, two molecules of toluol lose six atoms of hy- 
drogen, and are converted into anthracene. 

C6H5-CH3 Cen^^CH 

— .3H2 = I 

C6H5-CH3 CeiH^CH 

2 mol. toluol. Aiithiaceue. 

In the pure state, anthracene forms rhombic tables, derived 
from an oblique rhombic prism. The crystals are colorless, 
and present a magnificent blue fluorescence (Fritzsche). They 
melt at 213°, and distil without alteration at about 360°. 

By the action of oxidizing agents, such as chromic acid, an- 
thracene is converted into a solid body, which crystallizes in 
beautiful yellow needles, fusible at 273°, and which can be 
sublimed without alteration. It is anfhraqimione, C^^H^O^, a 
body which bears the same relations to anthracene as quinone 
to benzol. 



C'W 


(.UJJIO 


Benzol. 


Anthracene. 


C«H^O^ 


QUIIBQ2 


Quinone. 


Antliraquinone. 



By treating antliraquinone with bromine, Graebe and Lieber- 
mann converted it into dibromanthraquinone, G^^H^Br'^O'^, a 
solid body, which crystallizes in yellow needles. 

Phenanthrene. — Besides anthracene, there is another hydro- 
carbon of the same composition, which exists in coal-tar, and 
may also be formed artificially. It is called phenanthrene, and 
forms colorless scales, having a bluish fluorescence. It melts 
at 100°, and boils at 340°. It is soluble in 50 parts of alco- 
hol at 13° : verv soluble in hot alcohol, and in ether and 



very 



benzol. 

ALIZARIN. 

CUH80* = Ci4H6(OH)202 

Natural State and Synthesis. — Alizarin is the name applied 
to the coloring matter of madder which Robiquet was the first 
to extract in a pure state. Graebe and Liebermann have re- 
cently made its synthesis by heating dibromanthraquinone to 
200° with potassium hydrate. 

54^ 



64:2 ELEMENTS OF MODERN CHEMISTRY. 

C^H^Br^O^ + 2K0H = 2KBr + C^*H«(OHyO^ 

Dibroniiintliraqiiiiione. Alizarin. 

This reaction, slightly modified, has become within a few 
years the base of an important industry. 

Ali-zarin does not exist ready formed in the madder plant. 
The latter contains a glucoside to which Robiquet has given 
the name ruber i/tJu-ic acid, and which is decomposed by the 
action of acids into alizarin and glucose. 

Euberytliric acid: Alizarin. Glucuse. 

Preparation.— Alizarin may be extracted from madder by 
boiling the latter with a solution of alum. The filtered liquid, 
left to itself for some days, deposits impure alizarin as a brown- 
red precipitate, and holds in solution another coloring matter 
which is caWed pirrpur in. 

The precipitated alizarin is purified by washing with dilute 
hydrochloric acid, and crystallization in alcohol. The product 
thus obtained is exhausted with a boiling solution of alum, 
which removes the purpurin,:and is finally dissolved in ether, 
which deposits it in crystals. 

To prepare artificial alizarin from anthracene, that hydro- 
carbon is first transformed into anthraquinone, and the latter 
body is treated with sulphuric acid to convert it into disulpho- 
anthraquinonic acid, which is then heated with an excess of 
potassium hydrate. 
C^^H«(SO^K)^0^ + 2K0H ^ C^^H''{0H)20^ + 2K-^S0^ 

Potassium Alizarin, 

disulphoanthraquinonate. 

The alkaline mass is dissolved in water, precipitated by hy- 
drochloric acid, and the precipitate purified by crystallization 
in alcohol and finally by sublimation. 

The artificial product is delivered to commerce in the form 
of a paste, but the reaction by which it is formed produces, at 
the same time, isomerides which remain mixed wit|pPhe aliza- 
rin, properly so called. Eight isomeric compounds are known 
having the composition C^^H^O*. One of them, purpuroxan- 
thin, is contained in small quantity in madder. 

Properties of Alizarin — x\lizarin forms long, brilliant, 
orange-yellow prisms. It is scarcely soluble in cold water, but 
dissolves somewhat better in boiling water, and is soluble in 
alcohol, ether, and carbon-disulphide. Between 215 and 225°, 
it sublimes in long, orange-yellow needles. It dissolves in sul- 



PURPURIN — NATURAL ALKALOIDS. G 13 

phuric ticid with ii blood-red color, and water precipitates it 
without alteration from this solution. Boiling dilute nitric 
acid converts it into oxalic and phthalic acids. When alizarin 
is heated to redness with zinc powder, it is reduced to anthra- 
cene (Graebe and Lieberniann). 

Alizarin forms combinations with the bases ; it dissolves in 
ammonia, with a purple color, and in the caustic alkalies, yield- 
ing purple solutions which have a blue reflection. 

Uses. — Alizarin produces a red color on fabrics that are mor- 
danted with alumina, and a violet on those which are mor- 
danted with ferric oxide. It is the coloring principle of madder 
and of the commercial product known as gamncui. The latter 
product is obtained by heating powdered madder with sulphu- 
ric acid to 100°, and exhausting the mass with water. The 
residue is garancin. 

PURPURIN. 

Ci*H5(OH)302 

This name is given to another coloring matter which may be 
extracted from madder, and which has already been mentioned. 
It appears to exist in the plant as a glucoside. It dissolves 
readily in alcohol and ether, with a red color. 

It crystallizes from weak alcohol in orange-colored needles, 
which contain one molecule of water of crystallization. From 
concentrated alcohol, it deposits in red, anhydrous needks. 
When heated, it melts and sublimes in red needles. 

Purpurin is an oxyalizarin, or a trioxyanthraquinone, C"H^ 
(0H)"^0^ : indeed, it may be obtained by treating a solution of 
alizarin in concentrated sulphuric acid with an oxidizing agent, 
such as manganese dioxide (de Lalande). Inversely, the reduc- 
tion of purpurin reproduces alizarin (Rosenstiehl). It under- 
goes a complete reduction, and is converted into anthracene, 
when heated with zinc-dust. 

Independently of the purpurin just described, there are three 
other compounds isomeric with it. 



NATURAL ALKALOIDS. 

The alkaloids are nitrogenized substances capable of uniting 
with the acids, like ammonia, and forming with them definite 
combinations wdiich constitute true salts. A large number 



644 ELEMENTS OP MODERN CHEMISTRY. 

of these compounds can be formed artificially, and arc derived 
directly from ammonia by the substitution of organic radicals 
for the hydrogen of that body. They are the compound, or 
substituted ammonias, and their constitutions are perfectly 
known. This is not, however, the case with the natural alka- 
loids, which have been discovered in many plants and vege- 
table products, and which often constitute the active principles 
to which these products owe their medicinal virtues. By anal- 
ogy, it may be inferred that these bodies also are derived from 
ammonia, like the compound ammonias. 

In 1800, the basic nature of one of the crystallizable princi- 
ples of opium was discovered by Sertiirner, but his discovery 
was unnoticed until 1817, when he published it in a treatise 
on morphine. Among the more important discoveries in this 
class of compounds must be mentioned those of strychine, 
brucine, and especially quinine, discoveries which are due to 
Pelletier and Caventou (1820). 

All of the alkaloids contain nitrogen. They are divided into 
two classes, the first of which includes the liquid and volatile 
bases, and the second the solids. The latter generally contain 
oxygen, the former do not. The alkaloids possess one charac- 
teristic property which indicates their analogy with ammonia. 
With platinic chloride their hydrochlorides form double salts, 
which are sometimes insoluble in water, sometimes soluble and 
crystallizable. 

If a solution of platinic chloride be poured into a solution 
of quinine hydrochloride, a yellow prec^jutate is at once formed; 
it is a combination of platinic chloride and quinine hydrochlo- 
ride, and is sometimes called quinine chloi*^latinate, or platino- 
chloride. ^'' 

CONINE. ■ 

C8H15N 

This is a liquid and volatile alkaloid which is extracted from 
the hemlock ( Conium macidatuin). The seeds of this tree are 
crushed and distilled with sodium hydrate. The alkaline li(juid 
which collects in the receiver is neutralized by dilute sulphu- 
ric acid, evaporated to a syrupy consistence, and the residue 
exhausted with a mixture of alcohol and ether, which dissolves 
the Conine sulphate, and leaves ammonium sulphate. The alco- 
hol and ether are driven out by evaporation ; a concentrated 



NICOTINE. 645 

solution of sodium liydrate is added to the coninc sulphate, and 
the liquid is distilled. The conine passes with a certain (pian- 
tity of water, on which it floats. It is separated, dried over 
some fragments of calcium chloride, and rectified in a vacuum. 

Conine is a limpid, oleaginous liquid, having a penetrating 
and nauseating odor, recalling that of hemlock. It boils at 
108°. It is slightly soluble in Avater, more so in cold than 
in hot water, so that a cold, saturated solution becomes clouded 
when heated. It is very soluble in alcohol and in ether. It 
has a strongly alkaline reaction, immediately restoring the blue 
color to reddened litmus-paper. It precipitates many metallic 
oxides from solutions of their salts. On contact with the air 
it becomes brown and resinified. 

Conine is often mixed with methylconine, a compound de- 
rived from conine by the substitution of a methyl group for 
an atom of hydrogen (Planta and Kekule). 

Wertheim has obtained from the flowers and seeds of the 
hemlock a solid alkaloid, which he has named conhydrine^ 
C^H^'NO, and which contains the elements of conine plus a 
molecule of water. 

Hugo Schiff" has recently made the synthesis of an isomeride 
of conine, w^hich he cAh paraconine. 

NICOTINE. 

C10]^14O2 

This alkaloid exists in tobacco. It may be obtained by ex- 
hausting tobacco with boiling water and evaporating the liquid 
to a syrupy consistence on a w^ater-bath ; the still hot extract 
is then mixed with twice its volume of alcohol, alloAved to settle, 
and the alcoholic liquid separated from the thick lower layer, 
which contains much calcium malate. The alcohol is distilled 
off", ^d the residue exhausted with strong alcohol, of Avhich 
tt>e gTeater part is then driven off" by evaporation. Potassium 
hydrate is added to the alcoholic extract, w^hich is then agitated 
\\\t\\ ether, which dissolves the nicotine set free. A few grammes 
of oxalic acid added to the ethereal solution causes the separa- 
tion of a syrupy deposit which contains oxalate of nicotine. 
This salt is decomposed by potassa, and the nicotine set free is 
dissolved out by ether. After the ether has been expelled on 
a water-bath, the nicotine is distilled in a current of hydrogen, 
that part being retained which passes above 180° (Schlocsing). 



04(3 ELEMENTS OF MODERN CHExMISTRY. 

Properties. — Nicotine is a colorless liquid, having an offen- 
sive, penetrating odor. It rotates the plane of polarization to 
the left. It boils between 2-iO and 2o0°, not, however, with- 
out undergoing partial decomposition. Above 14(5°, it begins 
to distil slowly, and at lOU^ it emits white vapors ; at ordinary 
temperatures it gives off so much vapor that a rod wet with 
hydrochloric acid will be enveloped in white fumes if held a 
little distance above the nicotine. 

Nicotine dissolves in all proportions in water, alcohol, and 
ether. It has a strongly alkaline reaction, and perfectly neu- 
tralizes the acids, and precipitates the metallic oxides from 
solutions of their salts. It is one of the most violent poisons 
known. 

ALKALOIDS OF OPIUM. 

Opium is the thickened juice of the capsules of the white 
poppy {Papciver somiiiferum). It is obtained by making in- 
cisions in these capsules from the base to the summit. A milky 
juice exudes, and in the course of a day thickens and solidifies 
in tears. These are removed, pressed together, and fashioned 
into variously-formed masses. 

Opium contains a number of alkaloids combined with several 
acids. Among the latter are a syrupy acid, to which Ander- 
son gave the name thcholactic acid, but which has recently 
been recognized to be identical with lactic acid (Buchanan), 
and mecoiiic acid, of Avhich the composition is expressed by 
the formula C^H*0^ The latter is one of the more important 
constituents of opium ; it possesses the characteristic property 
of producing a blood-red color with ferric salts. Opium con- 
tains also a gummy matter, soluble in water, and a brown, in- 
soluble, resinous matter, which remains in the mass when 
opium is exhausted with water. The aqueous solution of opium 
has a brown color. The following alkaloids have been obtained 
from opium : 

Morphine Cimi9N03 

Codeine CisiPiNQS 

Thebiiinc Ci91l2'N03 

Papaverine C^iH'^iNO* 

Narcotine C'^ir^^iNQT 

Narceine C23U'^»N09 

Besides these, Merck has described another alkaloid of opium 
under the name porphyroxiae ; but, according to Hesse, this 



MORPHINE. G47 

body is a mixture of several bases, to which he lias given the 
names nieajiiidine, laxdanine, codamine^ and huitliopinc. 

Opium sometimes contains an alkaloid which is designated 
as i^scudomorphine, and which is oxymor})hine, C^^H^^NO^ 

Independently of these alkaloids, a neutral, crystallizable 
substance has been extracted from opium, and called meconine, 
Qio£|u)Qi Q^ .^jj these bodies, we will only consider morphine, 
codeine, and narcotine. 

MORPHINE. 

CnHi9N03 -f H20 

Preparation. — 1. Opium is cut into slices and exhausted 
with water. The solution is evaporated to a syrupy consistence 
and the still hot extract is mixed with an excess of pulverized 
sodium carbonate. After the lapse of twenty-four hours, the 
precipitate is collected and exhausted with dilute acetic acid, 
which dissolves the morphine and leaves the narcotine. The 
liquid is jfiltered, decolorized by animal charcoal, and super- 
saturated with ammonia. The morphine is precipitated, and 
is purified by crystallization in alcohol (Merck). 

2. One kilogramme of opium is exhausted with cold water ; 
100 grammes of pure lime are added to the liquid, which is 
then evaporated to a syrupy consistence at a temperature of 65 
or 75°. After cooling, the mass is exhausted with 3 litres of 
water which leaves the meconate of calcium ; the latter is 
separated by filtration. The liquid is then evaporated to one- 
fourth its volume, and while it is still hot, 50 grammes of 
calcium chloride dissolved in 100 grammes of water and 8 
grammes of hydrochloric acid are added. 

This mixture is left to itself for about two weeks, when it 
will be found to have set in a mass of crystals which are bathed 
in a colored mother-liquor. The deposit is pressed in a cloth, 
dissolved in boiling water, with addition of animal charcoal, 
and the solution filtered. On cooling, a mass of crystals is 
formed, consisting of a mixture of morphine hydrochloride and 
codeine hydrochloride. These are pressed, dissolved in water, 
and ammonia is added, which precipitates the greater portion of 
the morphine, while the codeine remains in solution. The 
deposit is collected on a filter and redissolved in boiling alcohol, 
from which the morphine crystallizes on cooling (liobertson 
and Gregory). 



648 ELEMENTS OF MODERN CHEMISTRY. 

Properties. — Morphine crystallizes in small, colorless, right 
rhombic prisms, having a bitter taste. It is insoluble in ether, 
in chloroform, and in benzol. The alcoholic solution rotates 
the plane of polarization to the left. The crystals contain one 
molecule of water which they lose at 100°. Morphine dis- 
solves easily in a solution of potassium hydrate ; it is very 
slightly soluble in ammonia ; almost insoluble in water. 

Tests. — 1. If a few drops of a solution of iodic acid be added 
to an alcoholic solution of morphine, the liquid immediately 
assumes a brown or yellow color, due to the liberation of iodine. 
Iodic acid exerts an oxidizing action on morphine. 

2. If a small quantity of morphine in powder be added to a 
solution of ferric chloride, a blue color is produced. 

3. Nitric acid produces an orange-red color with morphine. 
The last two reactions are characteristic. 

AVhen morphine is heated to 200° with potassium hydrate, 
it disengages methylamine. 

Morphine Hydrochloride. — This salt, of which the prepara- 
tion has already been indicated, crystallizes in silky needles, 
soluble in 1 part of boiling and 16 or 20 parts of cold water ; 
it is very soluble in alcohol. The crystals contain C^^H^^NO'^ 
HCl + 8H^0. 

Platinic chloride forms a yellow precipitate of a double chlo- 
ride in an aqueous solution of morphine hydrochloride. 

(C^^H^»NOlHCl)-.PtCl* 

Hydrochloride of morphine is much used in medicine. 

When its solution is heated to 60° with silver nitrite, the 
base is oxidized and converted into oxymorphine, C^^H'^NO*. 

When morphine is heated to about 140° with concentrated 
hydrochloric acid, it is transformed into a new base, apomor- 
phnie, C^'^H^'NO^, derived from morphine by the removal of 
one molecule of water (Matthiessen). This base possesses 
special therapeutic properties. When administered by hypo- 
dermic injection or swallowed, it acts as an emetic. 

CODEINE. 

C18H21N03 + H-^0 

Codeine is methylmorphine. It is obtained from the am- 
moniacal mother-liquor from which the morphine is deposited, 
in the preparation of the latter body by the process of llobcrt- 



NARCOTIXK. G49 

son and Gregory. For tliis purpose, the ni()tlier-li(|uor is eon- 
eentrated and caustic potassa is added, wliicli })recipitates tlie 
codeine. It is collected, dissolved in liydrocldoric acid, tlie 
solution decolorized with animal charcoal, and the codeine again 
precipitated by potassa. Lastly, the preci})itate is dissolved in 
ordinary ether, which deposits the codeine in voluminous crys- 
tals by spontaneous evaporation. 

These crystals are right rhombic prisms, and contain one 
molecule of water. Anhydrous ether deposits codeine in anhy- 
drous rectangular octahedra. 

Codeine dissolves in 89 parts of water at 15°, and is more 
soluble in boiling water. Alcohol and ether dissolve it readily, 
and the alcoholic solution rotates the plane of polarization to 
the left. 

If bromine-water be poured upon codeine in fine powder, 
the latter dissolves, and is converted into hydrobromide of 
monohromo-codeine. By the continued addition of bromine- 
water, a yellow precipitate is formed, consisting of hydrobro- 
mide of tribromo-codeiRe, that is, codeine in which three atoms 
of hydrogen are replaced by three atoms of bromine. 

NAKCOTINE. 

C22X123XOT 

Narcotine may be extracted from the residue of opium which 
has been exhausted by water. This is treated with hydrochloric 
acid, filtered, and the filtrate precipitated by sodium carbon- 
ate. The precipitate is dissolved in alcohol, and the alcoholic 
solution decolorized by animal charcoal. The narcotine crys- 
tallizes out on cooling. 

It forms brilliant, colorless prisms, belonging to the system 
of the right rhombic prism. It melts at 70°. It is insoluble in 
cold water, and requires for its solution about 60 parts of cold 
absolute alcohol, or 12 parts of boiling absolute alcohol. It is 
soluble in ether, a character wdiich distinguishes it from mor- 
phine. Its alcoholic and ethereal solutions have a bitter taste, 
and turn the plane of polarization to the left. 

If a few crystals of narcotine in a watch-glass be moistened 
with sulphuric acid containing a trace of nitric acid, an intense 
blood-red color is produced. 

By the action of certain oxidizing agents, narcotine is de- 
2c 55 



650 ELEMENTS OF MODERN CHEMISTRY. 

composed into a new alkaloid, cotarnine, and an acid which is 
called opianic acid (Wohler). 

Narcotine, Opiuiiic acid. Cotarnine. 

Cotarnine crystallizes in colorless, silky needles, grouped in 
stars. 

When subjected to the action of hydriodic acid, narcotine 
loses successively three methyl groups, and yields hydriodides 
of three new bases. One of them contains CH^'NO^, and has 
been designated as nornarcotine or normal narcotine. It is 
formed according to the equation 

C^H^^NO^ -f SHI = G^^H^'NO^ -f SCH^I 

Narcotine. Nornarcotine. Methyl iodide. 

Hence narcotine itself represents trimethyl- nornarcotine, 
Q^m^\(^Wf^O' (Matthiessen and Foster). 

The intermediate terms between narcotine and nornarcotine 
are also known, 

ALKALOIDS OF CINCHONA. 

The different cinchona barks owe their febrifuge virtues to 
several alkaloids, of which the more important, quinine and cin- 
cJionine, were discovered by Pelletier and Caventou in 1820. 
Since then, quinidine and cinchonidine have been isolated, the 
first isomeric with quinine, the second with cinchonine. All 
of these are crystallizable alkaloids. When their sulphates are 
heated with sulphuric acid, they are converted into two new 
isomerides, quinicine and cinchonicine. The latter are not crys- 
tallizable. 

Hence the following six alkaloids are known : 

Cinchonine, cinchonidine, cinchonicine . . . C^TIZ'tN^O 
Quinine, quinidine, quinicine C^'^II'^^N^O^ 

These alkaloids are by no means distributed in the same 
manner in the numerous species and varieties of cinchona bark, 
and these barks are not equally rich in alkaloids. The follow- 
ing summary gives some indications of this difference : 

1 KILOGRAMME OF RARK YIELDS : 

YgWow hark {Cinchona Cali'Hai/(() . . 
Rod hark {Cinchona siiccirubra) . . . 

Loxa {Cinchona coudami- 
Pale bark ■{ ueo) 

Iluanuco (CVucAoHa riitida) 



QiriXINE SULPHATE. 


CINCHOMNE 
SULPHATE. 


30-82 g 


rainmes. 


6-8 


grammes. 


20-25 


" 


8 


" 


8 


u 


fi 


It 


6 


« 


12 


« 



QUININE. 651 

In the cinchonas, these alkaloids arc combined with a well- 
defined, crystallizable acid, whose composition is expressed by 
the formula C'lr-'O^. It is qiiinic (icid. 

This acid is obtained from the calcium quinatc which is de- 
posited in a few days, wdien the liquid separated from the quino- 
ealcium precipitate is concentrated and allowed to stand (see 
farther on). 

This calcium quinate is purified by several crystallizations, 
and its solution decomposed by oxalic acid. The quinic acid 
remains in the solution, and separates in crystals when the 
liquid is properly concentrated. 

Quinic acid crystallizes in beautiful, transparent, oblique 
rhombic prisms. It is very soluble in water, and but sli<>htly 
soluble in absolute alcohol. It melts at 1G1.5°, losing at the 
same time the elements of water. 

Its aqueous solution rotates the plane of polarization to the 
left. 

Its composition corresponds to the formula C^IF^O". When 
distilled with a mixture of sulphuric acid and manganese diox- 
ide, it yields cjuinone, C^IPO'^. 

A substance is also found in cinchona bark which is called 
quinotannic acid. It belongs to the tannin group, and is a 
glucoside. Hlasiwetz states that it can be decomposed into 
glucose and cinchonine red., a substance noticed by Pelletier and 
Caventou as produced during the preparation of quinine. 

QUININE. 

When ammonia is added to a solution of sulphate of quinine, 
a white precipitate of quinine is obtained, which, when left to 
itself and moistened with water from time to time, becomes 
crystalline by combining with one molecule of water. 

Quinine is very bitter. It dissolves in 2266 parts of cold, 
and in 760 parts of boiling water; in 1.33 parts of cold alco- 
hol, and 22.6 parts of ether (J. Eegnauld). It is also soluble 
in chloroform. Its alcoholic solution turns the plane of polar- 
ization to the left. AVhen water at 32° is added to the hot 
alcoholic solution until a cloud begins to form, resinous quinine 
is deposited, and also colorless, prismatic crystals containing 
three molecules of water. 

auinine Sulphate, 2(C^"H2*N^O').SO*H^ + m:'0,— Prep- 



652 ELExMENTS OP MODl^llN CHEMISTRY. 

ration. — This salt, which is extensively used in medicine, is 
prepared by boiling yellow bark {Cuichona Cal isaT/a) or red 
bark (^Cuichona siiccinihra) with water acidulated with sul- 
phuric or hydrochloric acid. A slight excess of milk of lime 
is then added in small quantities to the decoction, and precip- 
itates not only the quinine and cinchonine, but all of the color- 
ing matter (cinchonine red), which forms an insoluble com- 
pound with the lime. The quinic acid remains in solution as 
calcium quinate. The quino-calcium deposit contains also the 
excess of lime, and calcium sulphate, in case sulphuric acid 
has been employed. It is collected on a cloth, allowed to drain, 
pressed, and dried. It is then exhausted with boiling alcohol, 
which dissolves out the alkaloids. 

The alcoholic solution, concentrated by distillation, deposits 
the cinchonine in crystals, in case the bark employed be rich 
in that alkaloid. The mother-liquor retains the quinine. It 
is neutralized by sulphuric acid, and the alcohol distilled oiF. 
The quinine sulphate crystallizes in a mass on cooling, and is 
purified by redissolving it in boiling water and adding animal 
charcoal. 

It has been proposed to replace the alcohol, in the extrac- 
tion of the quino-calcium deposit, by certain fixed or volatile 
oils, which dissolve quinine. For this purpose, petroleum and 
the heavy oils produced by the distillation of tar, and which are 
abundant in commerce, may be used with advantage. After 
having dissolved the alkaloids in these oils, the solutions are 
agitated with dilute sulphuric acid, which removes from them 
the quinine and cinchonine. Sulphates are thus obtained which 
may be crystallized. 

Properties. — Quinine sulphate occurs in long, thin, light 
needles, which are somewhat flexible. It requires for its solu- 
tion 740 parts of water at 13°, or about 30 parts of boiling 
water. The solution restores the blue color to reddened litmus- 
paper. It turns the plane of polarization to the left (Bouchar- 
dat). When crystallized in alcohol, quinine sulphate contains 
only two molecules of water. 

If some quinine sulphate be suspended in cold water, and a 
few drops of sulphuric acid be added, the sulphate dissolves 
and the liquid ac(juires a blue fluorescence. 

In this case, quinine sulphate, which is a basic salt, is con- 
verted into a salt, C-'"H''N'0'.SO'ir', which has an acid reac- 
tion, and is called quinine acid sulphate. This salt crystallizes 



CINCIIONINE. G53 

with 7 molecules of water. A .still more acid sulphate is known, 

c^"n-\\-W(S(Vir^)^ -f Tir-'o. 

If an excess of chlorine-water be added to a solution of 
quinine sulphate, and the liquid be supersaturated with ammo- 
nia, a beautiful green color will be produced. 

This reaction is characteristic of (juinine. 

When tincture of iodine is added to a solution of ((uinine 
sulphate in hot acetic acid, in a few hours the liquid deposits 
large, thin plates. It is iodoquudne sulphate, (J'"H'*N-0'P. 
S0*H2 + 5H-'0 (Herapath). 

These crystals appear green by reflected light, and are almost 
colorless by transmitted light. When two of them are crossed, 
the portions which are superposed almost entirely intercept the 
passage of light. In this respect, iodoquinine sulphate acts 
as a polarizer, like tourmaline. 

Uses. — Quinine sulphate is a valuable remedy. It is prin- 
cipally employed as a febrifuge, and generally in the treatment 
of diseases of an intermittent type. It is successfully admin- 
istered in other diseases, especially in acute articular rheuma- 
tism, gout, certain neuralgias, etc. 

CINCHOXINE. 

Cinchonine is obtained as an accessory product in the manu- 
facture of quinine. It deposits from its alcoholic solution in 
brilliant, colorless, quadrilateral prisms. It is insoluble in 
water, but soluble in alcohol and chloroform. It is almost 
insoluble in ether, a property which distinguishes it from qui- 
nine. Its alcoholic solution turns the plane of polarization to 
the right. 

Cinchonine has a bitter taste. It melts at 170°, and when 
cautiously heated in the bottom of a closed tube, it partly sub- 
limes in very light, delicate crystals. When treated with a 
dilute solution of potassium permanganate, it forms various 
substitution products, and a new base remains, less oxidizable 
than cinchonine. It is hydrochiclioiiine. Caventou and Willm 
consider that this base is contained, in the state of mixture, in 
commercial cinchonine. 

By oxidizing cinchonine with nitric acid, Weidel has ob- 
tained a series of acids, one of which contains nine atoms of 
carbon ; it is quinolic acid, C^H'^N'^O*, wdiile two others contain 



654 ELEMENTS OF MODERN CHEMISTRY. 

each eleven atoms. Lastly, the fourth of these acids, cinchomc 
acicl^ has the composition (T'°H^*N''^0^ When (listilled, it yields 
a non-nitrogenized acid, C^°H*"0^, i^yrocinchouic acid, which is 
an isomeride of opianic acid. 

STRYCHNINE AND BRUCINE. 

Pelletier and Caventou discovered these two alkaloids in 
various vegetable products derived from plants belonging to the 
genus Stri/chnos, such as nux vomica (seeds of the Strychnos 
Nux vomica), flilse angustura bark, which comes from the same 
Strychnos, Saint Ignatius bean (seeds of the Strychios Ignatii), 
etc. These alkaloids, to which 'igasurine has recently been 
added (Desnoix), appear to be combined in the Strychnos with 
an acid but little known, which Pelletier and Caventou called 
igasuric acid. 

Strychnine, C'-^H^^N-Ol — Preparation. — Strychnine is ex- 
tracted from nux vomica by a process analogous to that which 
serves for the preparation of quinine. The crude strychnine 
which deposits in crystals from its alcoholic solution is always 
mixed with brucine. The two alkaloids are separated by con- 
verting them into nitrates, which are made to crystallize ; the 
strychnine nitrate, less soluble than that of brucine, deposits 
in needles, and the concentrated solution afterwards deposits 
voluminous crystals of brucine nitrate. To isolate the alka- 
loids, the corresponding nitrates are precipitated by ammonia, 
and the alkaloid dissolved in boiling alcohol, which deposits it 
in crystals on cooling. 

Properties. — Strychnine crystallizes in rectangular octa- 
hedra, sometimes in quadrilateral prisms terminated by four- 
sided pyramids. It is colorless and odorless, but extremely 
bitter. It is insoluble in water and in ether, and scarcely 
soluble in absolute alcohol. It dissolves readily in ordinary 
alcohol, in chloroform, and in the volatile oils. Its alcoholic 
solution turns the plane of polarization to the left. 

Strychnine is one of the most active poisons known ; even 
in very small doses it produces violent tetanic spasms. 

Brucine, C'^'H^''N-'0' -f 4IP0.— Brucine, separated from 
strychnine by the process above indicated, cr3'stallizes by slow 
evaporation of its solution in weak alcohol in obli(jue rhombic 
prisms, which are often quite large. These crystals, which 
contain four molecules of water, rapidly effloresce in the air. 



COCAINE— ACONITINE. 655 

Brucine is almost insoluble in water, but dissolves readily in 
alcohol and very slightly in ether. The alcoholic solution ro- 
tates the plane of polarization to the left. 

If brucine be moistened with nitric acid, it immediately 
assumes a blood-red color and, by the aid of a gentle heat, 
disengages carbon dioxide and vapors which contain methyl 
nitrite (Strecker). 

COCAINE. 

Cocaine was obtained by Niemann from coca leaves {^Ery- 
throxylon Coca). It has been studied by Wohler and Lassen. 

Preparation. — Coca leaves are exhausted several times with 
water at a temperature between (30 and 80°, and the solu- 
tion is precipitated by lead acetate, and filtered ; the filtered 
solution is freed from excess of lead acetate by addition of 
sodium sulphate and then, after a new filtration, the solution 
is evaporated. Sodium carbonate is then added until it pro- 
duces a faint alkaline reaction ; the liquid is lastly agitated 
with ether, which takes up the cocaine and leaves it on evapo- 
ration. 

Properties. — Cocaine crystallizes in oblique rhombic prisms 
of four or six sides, which are colorless and odorless, and fuse 
at 98^. It is but slightly soluble in cold water, more soluble in 
alcohol, very soluble in ether. Its taste is bitter, its reaction 
slightly alkaline. When heated with hydrochloric acid, it ab- 
sorbs two molecules of water and decomposes into methyl alco- 
hol, benzoic acid, and a crystallizable base, ecgonme^ C^H^^NO^ 
+ H^O. 

Cnjj2iN0^ _j_ 2W0 = C^H^^NO^ + CH*0 + C"H«0^ 
ACONITINE. 

C27H40KO10 

The Aconitum Napellus contains, independently of aconitic 
acid, a base which was extracted by Greiger and Hesse. It 
occurs as a white powder, or as colorless, tabular crystals, only 
slightly soluble in water, very soluble in alcohol. Its taste is 
acrid and bitter. It is a violent poison. Its nitrate crystal- 
tizes readily. 



656 ELEMENTS OF MODERN CHEMISTRY. 

ATROPINE. 

This alkaloid, which is largely used in the treatment of dis- 
eases of the eyes, was discovered in 1833 by Geiger and Hesse, 
and by Mein, in the belladonna, or deadly nightshade {Atropa 
Bclladonmi). Planta has shown the identity of atropine and 
dafuruie, which has been obtained from the thorn-apple 
(^Datura Stramoniimi). 

Preparation. — Belladonna-root is reduced to powder and 
digested several days with alcohol. The solution is filtered, 
slaked lime, in quantity equal to one-twentieth of the weight of 
root employed, is added, the solution again filtered, and rendered 
slightly acid with sulphuric acid. It is again filtered, and t of 
the alcohol distilled off. The residue is concentrated at a gentle 
heat, and a concentrated solution of potassium carbonate is added 
until the liquid, now neutral, begins to be clouded. After a few 
hours, the precipitate is separated by filtration, and potassium 
carbonate is added to the filtrate as long as impure atropine is 
precipitated. The next day, the deposit is collected on a filter, 
pressed, dried, and exhausted with 90 per cent, alcohol. The 
solution is decolorized with animal charcoal, the liquid diluted 
with five or six times its volume of water and put in a cool, 
dark place. The atropine is deposited in 12 or 24 hours in 
crystalline needles. 

Properties. — Atropine crystallizes in delicate needles, fusi- 
ble at 90°. It dissolves in 300 parts of cold water, and in 
almost all proportions of alcohol. It is less soluble in ether. 
At 140° it volatilizes, but the greater part of it is decomposed. 

In burning, atropine diffuses the odor of benzoic acid. When 
it is treated with potassium dichromate and suljdiuric acid, 
benzyl aldehyde distils and benzoic acid is formed (Pfeiffer). 

Atropine is a virulent poison. A solution of su/j)hafe of 
afropiite is used in medicine. A single drop, even of a very 
dilute solution of this salt, produces dilatation of the pupil. 

THEOBROMINE. 

C7H8N402 

Theobromine exists in the beans of the cacao ( Thcohroma 
Cacao). To prepare it, the crushed cacao beans are exhausted 



CAFFEINE — ALBUMINOID MATTERS. 657 

■with water, and tlio aqueous extract is ])recij)itate(l by lead ace- 
tate. Tlie i)recipitate is separated by filtration, and the tiltratc 
is freed from an excess of lead by hydrouen sulphide ; it is then 
again filtered, and evaporated to dryness. The residue is dis- 
solved in absolute alcohol and the solution concentrated ; the 
theobromine separates as a crystalline jjowder, havinti' 'i bitter 
taste, slinhtly soluble in alcohol and ether. It may be sublimed. 
It is soluble in ammonia. 

CAFFEINE, OR THEINE. 

Caffeine was extracted from coffee in 1821 by Pelletier and 
Caventou, and by Kobiquet and Runge. Liebig, Pfaff, and 
Wohler determined its composition. It exists in coffee, tea, 
Paraguay tea (leaf of the Ilex Faraguaiemis), and guarana 
(seeds of the PauUuua SorhiUs). The latter product contains 
5 per cent. Caffeine is methyl-thcobromine. 

Preparation. — Caffeine, or theine, is generally obtained 
from tea. Powdered tea is exhausted several times with cold 
alcohol, and the tincture is precipitated by subacetate of lead, 
filtered, and a current of hydrogen sulphide passed through 
the filtrate to precipitate the excess of lead. The filtered liquid 
is then evaporated to one-fourth its volume, neutralized by po- 
tassium hydrate, and allowed to crystallize (Herzog). 

Properties. — Cafi'eine forms long, silky needles, which are 
light and colorless. It loses its water of crystallization at 100°, 
melts at 178°, and sublimes without alteration at a higher tem- 
perature. It is only slightly soluble in cold water, but dissolves 
readily in boiling water, and in alcohol. It is but slightly soluble 
in etlier. It forms definite combinations with the acids. When 
boiled with concentrated potassa, it disengages methylamine. 

When caffeine is boiled for a few minutes with fuming nitric 
acid, the yellow liquid evaporated to dryness, and the residue 
moistened with ammonia, a purple color is produced, analogous 
to that of murexide. 



ALBUMINOID MATTERS. 

- The albuminoid matters are complex organic substances, con- 
taining carbon, hydrogen, oxygen, and nitrogen, which are often 
associated with a small proportion of sulphur. By their com- 
2c* 



658 ELEMENTS OF MODERN CHEMISTRY. 

position and properties they are allied to the coagulable matter 
which exists in white of e«zg and in the serum of blood, and 
which is called albumen. 

The epidermic productions and the insoluble substances 
which are converted into gelatin or chondrin by boiling, differ 
from albumen and its allied compounds by their composition. 
They contain less carbon and more nitrogen. For this reason 
the neutral nitrogenized matters of the economy are divided 
into two comprehensive classes, albuminoid substances proper, 
and those substances which resemble in composi^^ion the insol- 
uble matter which forms the cartilage of bones, and which 
yield gelatin by the action of boiling water. 

The more important of the albuminoid bodies are as follows : 

Albumen ... A nitrogenized matter, coagulablc by heat, and exist- 
ing in many li([uicls of the animal economy, particu- 
larly in Avhite of e.;g and the serum of blood. 

Fibrin .... A nitrogenized matter, which deposits in the solid state 
during the coagulation of blood. 

Casein .... A nitrogenized matter, existing in milk, and considered 
identical with albuminate of sodium. 

Globulin ... An albuminoid subitan^e that can be obtained from 
the red blood-corpuscles. 

Syntonin . . . An albuminoid sul).-itance, resulting from the action of 
very dilute hydrochloric acid on muscular fibres. 

Myosin .... An albuminoid body contained in muscular fibres. 

Vitellin .... The albuminoid matter of yolk of egg. 

Hemoglobin . . A crystallizable substance contained in red blood-cor- 
puscles. 

Among the cartilaginous and gelatinous substances are the 
following : 

Ossein, or collagene, which forms the cartilage of bones, and yields yclatin 

when boiled with water. 
Chondrogin, which constitutes the cartilage of the short ribs, and which 

yields chondrin when boiled with water. 
Keratin, or horny structure. 
Elastin, the constituent of elastic tissue. 
Fibroin, a product peculiar to silk-worms, etc. 

The substances belonging to these two groups possess the 
following elementary composition : 

Carbon 

Hydrogen 

Nitrogen 

Oxygen 

Sulphur 

100.0 100.0 



FIRST GROUP. 


SECOND GROUP. 


53.5 


50.0 


6.9 


6.6 


15.6 


16.8 


2.', to 22.4 


26.1 to 23.1 


I to 1.6 


0.5 to 3.5 



ALBUMINOID MATTERS. G59 

Of most of tlio albuminoid substances, two modifications 
are known, one .S()lu})l(' and tlio otlicr insoluble. Thus beat, 
acids, and alcohol convert soluble albumen into insoluble albu- 
men, and the latter a})j)ear8 to have the same, or very nearly 
the same composition after coaiiulation as before. 

The in.soluble albuminoid bodies, such as coa^uulated albu- 
men, cooked albumen, librin, and ciusein, dissolve by the aid of 
a uentle heat in potassium hydrate, to which they yield a 
portion of their sulphur. The alkaline liquid, suj)ersatu- 
rated with acetic acid, precipitates the dissolved matter in 
flakes. 

Concentrated and boiling solutions of the alkalies decompose 
all albuminoid substances, the principal products of the decom- 
position being carbon dioxide, formic acid, gli/cocol, and its 
homologue leucine, C'H'^NO", its well as a nitrogenized sub- 
stance known as tyrosine and containing C^11"X()'\ The other 
decomposition products will be indicated when treating of 
albumen. 

Leucine and tyrosine are also formed when albuminoid sub- 
stances are long boiled with dilute sulphuric acid, xVt the same 
time, a^spartic acid, and glutamic acid, C^IPNO^ which is the 
acid amide of normal pyrotartaric acid, is formed. 

^ ^^ <CO^H ^ ^^ ^- ^ ^"-CO^H 

Pyrotartaric acid. Glutamic acid. 

Concentrated hydrochloric acid dissolves the insoluble albumi- 
noid bodies, and the solution assumes a violet color, especially 
on contact with the air (Caventou). 

When brought into contact with water containing one or 
two thousandths of hydrochloric acid, insoluble albuminoid mat- 
ters swell up and are finally converted into a transparent jelly, 
which partially dissolves in water. 

By the action of energetic oxidizing agents, such as chromic 
acid, or manganese dioxide and sulphuric acid, albuminoid 
bodies produce various products of oxidation and decomposi- 
tion, among which we may note particularly : (1), the volatile 
acids of the series, C"H^"0'^, from formic acid to caproic acid 
inclusive; (2), the corresponding aldehydes; (3), the nitriles 
(hydrocyanic ethers), propionitrile (ethyl cyanide), and valero- 
nitrile (butyl cyanide) ; (4), benzoic acid and benzyl alde- 
hyde. 



660 ELEMENTS OF MODERN CHEMISTRY. 



ALBUMEN. 

Two irjodifications of al))uiiien are known : one is soluble, 
the other insoluble. 

Soluble albumen exists in solution in white of e<ip;, and in 
other liquids of the animal economy. The coauulable prin- 
ciple of the serum of blood is a li(|uid very analoiious to the 
albumen of white of egg ; some chemists have called it serin. 

When a filtered solution of white of egg is evaporated at a 
low temperature or in a vacuum, the soluble albumen at length 
dries to a transparent, yellowish mass, having a gummy appear- 
ance. In this state it is not pure ; it remains combined with 
a trace of alkali and mixed with a small quantity of salts. 
When treated with water, it again dissolves. When it is per- 
fectly dry, it may be heated to even 1 00° without losing all of 
its water. The greater part, if not all, of the salts which exist 
in white of egg with the albumen may be removed by dialysis 
(Graham). 

When a solution of white of egg or of the serum of blood 
is heated, the liquid begins to be clouded at 70°, and coagulates 
at about 73°, sometimes in flakes, sometimes in a white mass, 
according to the concentration of the solution ; heat converts 
albumen into the insoluble variety. 

When white of egg is diluted with eight or nine times its 
volume of water and the carbonic acid gas which is dissolved 
or combined with the albumen is carefully expelled at a low 
temperature, a solution is obtained which is not coagulable by 
heat. The lost property may, however, be restored by passing 
carbon dioxide through the liquid. 

It is generally considered that there is no difference of com- 
position between soluble and insoluble albumen. However, 
Schiitzenberger finds that the difference is sensible. If strong 
alcohol be added to a solution of albumen, a white coagulum is 
formed, which becomes insoluble in water by the prolonged 
action of alcohol. 

Action of Acids on AlJmmcn. — Sulphuric, hydrochloric, and 
nitric acids precipitate albumen in thick flakes, which retain a 
certain quantity of acid ; the latter may be removed by pro- 
longed washings with water. 

The action of nitric acid upon albumen is often used for the 
detection of that substance in pathological urine. A still more 



ALBUMEN. 661 

sensitive reagent is metaposphoric acid, which precipitates the 
smallest traces of albumen contained in a solution. 

Ordinary phosphoric acid, acetic acid, and lactic acid, do not 
precipitate solutions of albumen. 

Action of Alkalies on Alhnnicn. — When white of eug is 
beaten up witli a few drops of a very concentrated solution of 
potassium hydrate, it sets in a few minutes in a soft, trans- 
parent, semi-solid mass, from which the excess of potassa may 
be removed by washing with cold water. The residue is albu- 
minate of potassa, from which all of the excess of potassa may 
be removed by prolonged washings. This gelatinous albumi- 
nate of potassa dissolves in boiling water. Acetic acid precip- 
itates the albumen from the solution. 

When potassa is added to a solution of albumen, albuminate 
of potassa is form^jd in the same manner ; acetic acid precip- 
itates the albumen, which it renders insoluble, but the alkaline 
solutitni is not troubled by boiling. If a few drops of lead 
acetate be added to the liquid, the oxide of lead formed will 
remain dissolved in the excess of alkali. The liquid then 
blackens on boiling, for the sulphur contained in the albumen 
acts on the lead, forming lead sulphide. 

Insoluble albumen dissolves in the alkalies and alkaline car- 
bonates, forming albuminates. 

Albumen combines with calcium hydrate, as with potassa ; 
a mixture of white of egg and slaked lime constitutes a very 
hard cement. 

By subjecting albumen and its analogues to the action of 
an aqueous solution of barium hydrate at a temperature of 140 
or 150°, Schiitzenberger observed that these bodies decompose, 
by hydration, into ammonia, carbon dioxide, oxalic, sulphurous, 
and acetic acids (the latter three bodies in very small propor- 
tion), and into other products, which are mostly crystalliza- 
ble. These products are tyrosine and the acid amides of the 
fatty series C"H''"^^NO', from amidobutyric acid, C*H'(NH2)0', 
to amid-oenanthic acid, C^H^^(NH'^jO''^, inclusive. With these 
products are others which are also crystallizable, but contain 
less hydrogen ; lastly, more highly oxidized amides are formed 
in the same reaction, such as malamic, diamidocitric, aspartic, 
and glutamic acids. 

From these results, it may be inferred that albumen aijd its 
analogues contain the elements of urea, tyrosine, acid amides 
of the fatty series, and more oxidized amides analogous to as- 

56 



662 ELEMENTS OF MODERN CHEMISTRY, 

partic acid, all of these bodies being combined together, with 
elimination of water. The presence of a certain proi)ortion of 
a dextriniform body in the products of the decomposition of 
albumen permits the supposition that the complex molecule of 
the latter body contains also an amide of cellulose or an amy- 
laceous body. 

Action of the Salts on Albumen. — Many salts precipitate 
solutions of albumen. Acetate and subacetate of lead form 
dense precipitates of albuminate of lead. Cupric sulphate pro- 
duces a blue precipitate. Corrosive sublimate yields a white 
precipitate, even in very dilute solutions of albumen. The in- 
solubility of this precipitate explains the use of albumen as an 
antidote to corrosive sublimate. 

Solutions of albumen are not precipitated by solutions of 
sodium chloride or sodium sulphate, but when acetic acid is 
added to the mixture, a precipitate forms, lieciprocally, a solu- 
tion of albumen to which acetic acid has been added is pre- 
cipitated by solutions of sodium chloride and sodium sulphate 
(Panum). 

When incinerated, both soluble and insoluble albumen leave 
a residue of calcium phosphate from which it is almost impos- 
sible to free the albumen. 

FIBRIN. 

AVhen recently-drawn blood is left to itself, it coagulates 
spontaneously in a few minutes, and soon separates into a yel- 
low liquid called the serum, and a red coagulum, which is the 
clot. The clot contains the red corpuscles, imprisoned in an 
insoluble albuminoid matter. This matter is fibrin, and it is 
now considered to be formed during the coagulation at the ex- 
pense of two soluble substances, both of which exist in solution 
in the liquid portion of blood, which is called plasma. One of 
these substances is called fibrinogen, the other is the fibrino- 
plastic matter or 2^c(ra(/lobulin. These two bodies have been 
isolated : when they are mixed in presence of water and a 
certain proportion of sodium chloride, the whole dissolves at 
first and the liquid soon coagulates spontaneously ; the coagu- 
lum is fibrin (Hoppe-Seyler). 

However this may be, fibrin may be obtained in fibrous 
masses by beating fresh blood. The latter does not coagulate 
in this case, but the coagulable constituent attaches itself in 



MYOSIN. 6G3 

red flakes to the rods with wliitli the hlood is agitated. By 
washing these flakes in running water, they are freed i'loni the 
adhering red corpiiseles, and obtained in white or grayisli ehis- 
tic masses of a fil)rous a}>pearance. This substance is entirely 
insoluble in pure water, but dissolves in slightly alkaline solu- 
tions, and even, by the aid of a gentle heat, in solutions of 
certain salts which have an alkaline reaction. It decomposes 
hydrogen dioxide into oxygen and water. 

When left to itself during the heat of summer, it putrefies 
very rapidly, and is converted into a blackish li((uid, which 
contains albumen. Leucine, and butyric and valeric acids are 
formed at the same time. 

When treated with concentrated hydrochloric acid, fibrin 
dissolves, forming a blue solution. When still moist fibrin is 
introduced into w^ater containing one or two thousandths of 
concentrated hydrochloric acid, it swells and becomes trans- 
parent, forming a jelly. After some time it dissolves in the 
liquid, although with difficulty, and the solution then contains 
a substance wdiich appears to be identical with syntonin (see 
farther on). 

When fibrin, swollen by hydrochloric acid, is digested at 
about 40° with gastric juice, or with the ferment called iwpsm^ 
which may be obtained from that liquid, the fibrin entirely dis- 
solves and is converted into a soluble and dialyzable body called 
peptone. This body is formed during the digestion of albu- 
minoid matters. 

Under certain circumstances sodium chloride dissolves fibrin. 
When such a solution is dial^^zed, the salt passes into the exte- 
rior liquid, and there remains in the dialyzer a limpid solution 
having all the characters of a solution of albumen from egg 
(A. Gautier). 

MYOSIN. 

Kiihne has designated by this name the albuminoid matter 
which exists in solution in the sheaths of the muscular fibres 
(sarcolemma), and which has the property of coagulating spon- 
taneously after death, thus producing cadaveric rigidity. 

Myosin is insoluble in water as well as in a saturated solu- 
tion of common salt, but it dissolves in a solution containing 
ten per cent, of salt. It may be extracted from the muscles 
by the following process : the flesh is chopped up, and decolor- 
ized by washing with water ; it is then triturated with pul- 



GG-t ELEMENTS OF MODERN CHEMISTRY. 

verized common salt, and enough water is added to produce a 
10 per cent, solution of salt. After digestion for a few hours 
in the cold, the liquid is filtered and brought into contact with 
rock salt ; as the latter dissolves, it precii)itates the myosin in 
flakes. 

llecently-precipitated myosin dissolves in a ten per cent, 
solution of salt, but it loses this property by desiccation. Very 
dilute hydrochloric acid dissolves it, and soon transforms it 
into syntonin. 

SYNTONIN. 

This substance may be extracted from muscular tissue. The 
latter is hashed, washed with water, and suspended in a large 
quantity of water containing one-thousandth of hydrochloric 
acid. The particles of meat swell and dissolve abundantly in 
the liquid, which is then pressed through a cloth, filtered, ana 
exactly neutralized with sodium carbonate. The syntonin is 
precipitated in gelatinous, colorless flakes, which collect and 
dry upon the filter in elastic films. 

Syntonin dissolves in water slightly acidulated with hydro- 
chloric acid. It also dissolves in lime-water, and in a one per 
cent, solution of sodium carbonate. 

HEMOGLOBIN. 

This name is given to the crystalline matter which may be 
extracted from red blood-corpuscles, and which was first called 
liematocri/stalUne. 

Preparation. — Clotted blood is broken up and triturated 
with its own volume of water until it is entirely reduced. It 
is then passed through a cloth, and the liquid is frozen, or 
agitated with small quantities of ether until the corpuscles are 
dissolved. The thawed liquid, or that which has been treated 
with eth-cr, deposits a coagulum which imprisons all of the 
unbroken corpuscles. The liquid is filtered, rendei'ed slightly 
acid by acetic acid, and alcohol is added as long as the pre- 
cipitate first formed continues to dissolve. When cooled to 0° 
for several hours, the red liquid sets in a mass of crystals ; 
these are collected on a filter, pressed, and washed with dilute 
alcohol and water, both at 0^. They are purified by dissolving 
them in water at 40° and evaporating the solution in a vacuum, 
or by adding alcohol and cooling the li([uid to 0°. 



HEMOGLOBIN. 



GGf) 



Composition. — Hemoglobin so prepared litis about the same 
composition as albuinini)id bodies, but contains a little iron. 
According to Jloppo-Seylcr, its composition is 

Carbon 54.18 

Hydrogen 7.2 

Nitrogen lfi.2 

Oxygon 21.5 

Iron 0.42 

Suli)bur 0.7 

Properties. — Hemoglobin forms crystals which differ accord- 
ing to the blood from which they have been obtained. They 
generally belong to the type 
of the right rhombic prism. 
Those from human blood pre- 
sent, under the microscope, the 
forms indicated in Fig. 13:^. 
They are red, and doubly re- 
fracting. They contain water 
of crystallization. 

They dissolve in water, and 
more readily in slightly alkaline 
solutions. 

The red solution of hemo- 
globin (oxyhemoglobin) has 
an important optical property. 
When light which has trav- 
ersed a dilute ;5olution of hemo- 
globin is decomposed by a 
prism, the spectrum so formed show^s two black bands (absorp- 
tion bands) between Fraunhofer's lines D and E (Stokes). 

The crystals of hemoglobin contain oxygen which is weakly 
combined, and which may be removed by exposing the crys- 
tals in a vacuum (Hoppe-Seyler). Oxygenated hemoglobin is 
known as oxyliemfxjJob'ni^ and hemoglobin deprived of oxygen 
reabsorbs that gas when brought into contact with it. It is 
curious that carbon monoxide will expel the oxygen from hemo- 
globin, at the same time replacing it (CI. Bernard). The com- 
bination of hemoglobin and carbon monoxide is soluble in 
water. 

The solution of oxyhemoglobin yields its oxygen to certain 
reducing agents, such as hydrogen sulphide. Reduced hemo- 
globin gives an absorption spectrum containing one single band, 

5G- 




Fig. 132. 



66Q ELEMENTS OF MODERN CHEMISTRY. 

situated in a position between the two absorption-bands of oxy- 
henioiilobin. 

Hemoglobin decomposes hydrogen dioxide. It is very un- 
stable, and if the crystals be dried at a temperature above 100° 
they rapidly become altered. The aqueous solution decom- 
poses spontaneously in a few hours at 15°, or temperatures 
above that point. The acids, even the weak ones, favor this 
decomposition, which is manifested by a change of color, the 
fine red tint of the hemoglobin being replaced by a brown. In 
these cases, hemoglobin decomposes into an albuminoid matter 
(globulin), and a ferruginous pigment called hematin. At the 
same time, small quantities of fatty acids are set free (Hoppe- 
Seyler). 

Hematin. — This substance has received different names. 
Lecanu, who first studied it, named it liematosin. When prop- 
erly purified, it forms a blackish-blue, amorphous powder, which 
is quite stable, since it resists a temperature of 180°. It con- 
tains carbon, liydrogen, nitrogen, oxygen, and iron. When 
incinerated, it leaves 12.8 per cent, of oxide of iron. 

It is insoluble in water, alcohol, ether, and chloroform. It 
dissolves in the alkalies, in ammonia, and in the acids, and is 
readily soluble in ammoniacal alcohol and in alcohol containing 
hydrochloric acid. These solutions are reddish-brown. AVitli 
hydrochloric acid, hematin forms a compound which crystallizes 
in rhomboidal laminae ; the crystals are characteristic and may 
be recognized by means of the microscope (hydrochloride of 
hematin). 

Hematoidin. — This body is doubtless a product of the 
decomposition of hemoglobin. Yirchow found it in orange- 
colored crystals in the remains of old hemorrhages of the brain. 
It is also found in blood which has been exposed to air, and in 
extravasated blood in the Graefian follicles. It may easily be 
obtained from the yellow bodies contained in the ovaries of the 
cow, by triturating them with glass, and digesting for a few 
days with chloroform. After evaporation of the yellow chloro- 
form solution, the residue is treated with ether to dissolve out 
the fiit. 

Hematoidin crystallizes in small, orange-red, transparent 
prisms. It is insoluble in water and alcohol, slightly soluble 
in ether ; it is soluble in chloroform, which it colors golden- 
yellow. It presents certain analogies with bilirubin (page 
673). 



GLOBULIN — CASEIN — GELATIN. GG7 



GLOBULIN. 

Berzelius gave this iiuine to the coiiguhible albuminoid sub- 
stance which may be obtained from red blood-corpuscles, and 
which is now believed to be a product of the decomposition of 
hemoglobin. This, or an analogous substance, exists in the 
crystalline lens. It may be obtained by boiling the crystalline 
lens of tlie ox with water and filtering the li([uid. A solution 
of globulin is thus obtained. It much resembles albumen in 
its properties. When heated, it becomes clouded at 73^, but 
coagulates completely only at 93°. It is not precipitated by 
either acetic acid or by the alkalies, but when its acid or 
alkaline solution is neutralized, a precipitate is formed. A 
solution of globulin is precipitated by a current of carbon di- 
oxide. 

CASEIN. 

When an acid is added to milk, a thick precipitate is at once 
formed ; it is produced by the casein. The lactic acid which 
forms in milk by the fermentation of the milk-sugar, produces 
the same precipitation. The milk is then said to curdle. The 
precipitate consists of an albuminoid matter called casein, 
which is considered to be identical with coagulated albumen. 

Casein dissolves in alkaline liquids and even in certain alka- 
line salts, such as carbonate and phosphate of sodium. It 
exists in this state in milk, which is alkaline when fresh. 
When this solution of alkaline albuminate, to which the name 
soluble casein has been given, is evaporated, it becomes covered 
with a pellicle. Acetic acid precipitates it in flakes, combining 
with the alkali. It is also coagulated by the gastric juice, 
which is acid, and which contains a ferment known as pepsin. 
This ferment exists in rennet which is prepared from the 
fourth stomach of the calf, and which serves to coagulate 
skimmed milk in the preparation of cheese. Indeed, casein, 
more or less altered by putrefaction, is the basis of the different 
kinds of cheese. 

GELATIN. 

The bones contain a cartilaginous substance, which may be 
isolated by dissolving out the mineral salts, Avhich consist of 
calcium carbonate and phosphate, with hydrochloric acid. 



6G8 ELEMENTS OF MODERN CHEMISTRY. 

There remains a semi-transparent, elastic substance, which re- 
tains the form of the bone. This substance, which has been 
called ossciRj or collagene, is insoluble in cold water, but by 
prolonged boiling, or more rapidly by digestion with water 
heated to a few degrees above 100"^, it dissolves and forms a 
solution, which sets in a transparent jelly on cooling. The 
body formed by this transformation dissolves slightly in cold 
water, and abundantly in boiling water, and the hot solution 
forms a jelly on cooling. Hence the name gelatin. 

Other tissues of the animal economy may be converted into 
gelatin by boiling with water. It is so with the cellular tissue, 
the skin, the scales, and swimming-bladder of fishes. The 
swimming-bladder of the sturgeon, known in commerce as fish- 
glue, furnishes very pure gelatin by boiling with water. 

The substances which may*be converted into gelatin possess 
very nearly the same composition as gelatin itself; hence no- 
thing precise is known concerning the nature of the change 
produced in them by the action of boiling water. 

Dry gelatin occurs in transparent sheets, which are sonorous, 
and of which the color varies from yellowish to brown, accord- 
ing to their thickness and purity. 

The aqueous solution is precipitated in white flakes by alco- 
hol. The acids do not precipitate it, with the exception of 
tannic acid, with w^hich it forms a thick coagulum, a combina- 
tion of tannin and gelatin. This action of tannin on gelatinous 
matters is applied in the manufacture of leather, which is ob- 
tained by leaving fresh or green skins, previously swelled by 
soaking in water, in contact with tan, that is, coarsely-ground 
oak-bark, which is well known to contain tannin. 

When chlorine-water is added to a solution of gelatin, a 
white cloud is formed which an excess of chlorine converts 
into a white, flocculent precipitate. 

Solutions of gelatin are precipitated by platinic chloride 
and by corrosive sublimate, but not by alum or the salts of lead, 
copper, silver, etc. When boiled with dilute sulphuric acid, 
gelatin is converted into leucine and a substance to which 
Braconnot gave the name sugar of gelatin, and which is gly- 
cocol. 

Chondrin. — When the cartilages of the short ribs are boiled 
for a very long time with water, they dissolve, forming a liquid 
which sets in a jelly on cooling. This gelatinous matter is 
chondrin. It is distinguished from gelatin by the property of 



RESPIRATION. (HI!) 

its aqueous solution to form ])r{'(i})it;ites with all the acids, and 
-with a uToat luunbor of niotallic salts. Alum i'orms in it an 
abundant, tioeculent precipitate. 



The substances which have just been summarily dcscril)ed, 
and others w^hich form the lic|uids an dtissues of the animal 
economy, undergo various transformations in the organism. 
They are derived from the vegetable kingdom, which alone can 
elaborate such complex matters. They pass Avith the aliments 
into the animal organisms, which assimilate them, and this work 
of assimilation does not profoundly modify the nitrogenized 
matters. But once fixed in the tissues, they do not remain 
there indefinitely, for there is a continual change and renewal 
of the whole economy. They become unfitted for the re(juire- 
ments of life, and disappear in their turn, eliminated by that 
continual oxidation which makes of the body a permanent 
hearth of slow^ combustion. A notable portion of the oxygen 
which enters the lungs at each inhalation penetrates into the 
blood, and is converted in the capillary system and the intrica- 
cies of the tissues into carbon dioxide. This gas, which returns 
to the lungs wath the venous blood, is exhaled at each exhala- 
tion. Expired air contains 4 to 5 per cent, of carbon dioxide. 

The carbon dioxide eliminates the greater portion of the 
carbon contained in the organic bodies burned during the phe- 
nomenon of respiration. The hydrogen of these bodies is 
eliminated in the form of w^ater. But what becomes of their 
nitrogen ? In man, and a great number of the higher animals, 
it is eliminated in the urea contained in the urine. Such are 
the principal features of this grand function of respiration, the 
source of heat in all animals. 

But how is this slow oxidation which constitutes the object 
of respiration, as first shown by Lavoisier, accomplished? Are 
the organic matters ready to be oxidized and consumed at once, 
or does the oxidation take place in successive phases, so that 
there are a certain number of intermediate terms between the 
complex products which must disappear and the final products 
of their oxidation ? All facts lead to the adoption of the latter 
conclusion. Indeed, there are found in the tissues and liquids 
of the economy a great number of bodies having compositions 
more or less complex, and which are the products, and, as it 



G70 ELEMENTS OF MODERN CHEMISTRY. 

were, the testimony of a successive simplification, — of disas- 
similation^ as it is called. 

But it must not be supposed that all of the reactions which 
take place in the economy are phenomena of oxidation. Be- 
fore being definitely oxidized and rejected from the body, the 
ingested organic matters and those which form our humors and 
tissues, may undergo various transformations and sometimes 
molecular complications. In this respect, Dr. Ure's celebrated 
experiment is well known : having taken benzoic acid, he found 
hippuric acid in his urine. Analysis has shov>'n the presence 
in the animal economy of a multitude of more or less complex 
organic compounds, nitroganized and non-nitrogenized, having 
definite compositions, and which are the products of varied 
reactions. Such reactions take place in the blood and in the 
tissues, principally in glandular organs, such as the liver. As 
it would be impossible to consider all of these products of dis- 
assimilation, we can only briefly notice the more important. 

LECITHINE. 

C42H84N P09 

Gobley has given this name to a phosphorized fatty matter, 
before noticed in the brain by Vauquelin. It exists in the 
brain and in the nerves. There is a closely allied body, recently 
described by Liebreich, under the name protagon. 

Gobley extracted lecithine from yolk of egg. That substance 
is exhausted with a mixture of alcohol and ether, and an alco- 
holic solution of cadmium chloride is added to the solution 
obtained ; a white, flocculent precipitate is formed, and is puri- 
fied by washing with alcohol and ether. This precipitate is a 
compound of cadmium chloride and hydrochloride of lecithine. 
It is suspended in ether and decomposed by hydrogen sulphide : 
cadmium sulphide is precipitated and hydrochloride of lecithine 
remains in solution, and may be obtained on evaporation in a 
wax-like mass. When the alcoholic solution of this hydro- 
chloride is decomposed by silver oxide, the lecithine is set free, 
and remains, after evaporation, in the form of a homogeneous, 
translucent mass. Lecithine may also be precipitated by pla- 
tinic chloride instead of cadmium chloride (Strecker). 

Locithine and all of its compounds are very alterable. It 
docomposes rapidly when the alcoholic solution of its hydro- 
chloride is boiled with baryta-water ; oleate and palmitate of 



CHOLESTERIN. G71 

barium are precipitated, phosphoolyeoratc of barium is formcnl, 
and an organic base called ncurinc remains in solution Miieb- 
reich). 

Strecker represents this interesting decomposition by the 
equation 

C*21P^XP09 + 31120 = C^IPPOS + C5H15N02 + Cisip^Qs + CieiP^O'^ 
Lecithine. Pliospho- Neurinb. Oleic Palmitic 

glyceric acid. acid. acid. 

Neurine is an oxygenized base of which the constitution is 
known. It is the hydrate of trimethyl-hydroxethylene-ammo- 
nium (page 527). 

The chloride of this ammoniated base is formed by synthesis 
by the action of ethylene chlorohydrate on trimethylamine (A. 
Wurtz). 

Trimethyl-liydroxetliylene- 
aiiimonium chlmide. 

Neurine is identical with a base which Strecker obtained 
from the bile and designated as choline. 



CHOLESTERIN. 

C26H«0 

This body is largely diffused in the organism. It exists in 
the bile, and is the principal constituent of most biliary cal- 
culi. It is found also in small quantity in the scrum of blood, 
in the brain, in yolk of egg, pus, the liquid of hydrocele, etc. 

Its solubility in alcohol and especially in ether, and the 
facility with which it crystallizes from its solutions, permits 
its easy isolation. Cholesterin ordinarily deposits in thin and 
brilliant, rhombic plates. It melts at 145°, and can be sub- 
limed, out of contact with air, at 360°. 

It forms neutral compounds with acids, analogous to the 
ethers ; it seems to be a monatomic alcohol. 



The principal organic constituents of the bile are two com- 
plex acids, both nitrogenized, and one of which contains sul- 
phur. These are glycocholic and taurocholic acids. They are 



672 ELEMENTS OF MODERN CHEMISTRY. 

not contained in the bile of all animals, and arc generally ex- 
tracted from that of the ox. They enter into the composition 
of human bile, which contains in addition coloring matters 
of which the most important is bilirubin. We will briefly 
describe these bodies. 

GLYCOCHOLIC ACID. 

(J--?6H43>q-Q6 

This body exists in the bile in the form of sodium glycocho- 
late, which salt may be obtained in crystals from ox's bile. 
The latter is decolorized by animal charcoal, filtered, the 
liquid evaporated, and the residue perfectly dried and dissolved 
in absolute alcohol ; the solution is introduced into a flask, and 
ether is cautiously added so that the two liquids may not mix, 
but form two layers. The latter gradually mingle and the 
sodium glycocholate deposits in crystals (Plattner). 

When dilute sulphuric acid is added to a solution of this 
salt, a cloud is formed, and glycocholic acid is soon deposited 
in fine needles. 

This acid is only slightly soluble in water and ether, but dis- 
solves in alcohol. It is dextrogyrate (Hoppe-Seyler). By the 
action of hydrochloric acid, it is decomposed into cliolalic acid 
and glycocol (Strecker). 

C-^6H«N0« + IPO = (J'W'O' + eiPNO^ 

Gl.vcdcholic acid. Cliolalic acid. Gl.vcocol. 

Cholalic Acid exists in the amorphous state and crystallized. 
It deposits from its ethereal solution in four-sided prisms, 
beveled at the ends, and containing two molecules of water of 
crystallization. By boiling with acids, it is converted into a 
resinous body which Berzelius called dysli/sin. 

C24JJ40O5 ^ C-'^PP'^O^ -f 2H'^0 

Dyslysiii. 

TAUBOCIIOLIC ACID. 

C26H45NS07 

The sodium salt of this acid remains dissolved in the ethe- 
real solution from which sodium glycocholate has deposited. 
It has not yet been obtained crystallized. It is dextrogyrate. 
-AV hen boiled with dilute acids, or with alkalies, it breaks up 
into cholalic acid and taurine (Strecker). 



BILIlll HIN — HILIVERDIN. ^73 

TamoclK.lic aciil. Cholalic acid. Tamii.e. 

Tiiuriuc, which was discovered by Leopold Gmeliii, has 
ah-eiidy been described (page 528). 

BILIRUBIN. 

C'611i8N"^03 

This substance exists in human bile and in biliary calculi. 
It may be extracted from the latter, which contain it as calcu- 
lary pi^-ment. They are crushed, and exhausted, first with 
ether which removes the cholesterin, then with boiling water, 
and fi'nally with chloroform. The coloring matter remams in 
the residue as a calcareous combination ; this is decomposed 
by adding hydrochloric acid, evaporating to dryness, and ex- 
hausting^ Uie dried residue with chloroform. After evaporation, 
the chloroform solution leaves a residue which contains, inde- 
pendently of bilirubin, three other biliary pigments which we 
will only mention : biliprasin, bilifuscin, and bilihumin. Alco- 
hol dissolves the bilifuscin from this residue, and the new 
residue is exhausted with chloroform, which takes up the bili- 
rubin, which alcohol precipitates in orange-colored flakes from 
the chloroform solution. 

Bilirubin is obtained in small, dark-red crystals by evapora- 
tion of its solution in chloroform. It is insoluble in water, and 
very slightly soluble in ether and alcohol, but dissolves in chlo- 
roform, °b en zol, and carbon disulphide. It is very soluble m 
the alkalies, forming an orange-red solution, which becomes 
pure yellow on addition of water, and from which hydrochloric 
acid precipitates bilirubin. The ammoniacal solution of b.ili- 
rubin gives precipitates with calcium chloride, barium chloride, 
and lead acetate. 

BILIVEBDIN. 

C16H18N20* 

When a solution of bilirubin in sodium hydrate is agitated 
svith air, it absorbs oxygen and becomes green. Hydrochloric 
acid precipitates biliverdin from the solution. 

It is a bright green powder, insoluble in water, ether, and 
cliloroform, but solu))le in alcohol. It contains one more atom 
of oxygen than bilirubin. 

2d ^7 



G74 ELEMENTS OF MODERN CHEMISTRY. 

We may add tliat other coloring matters have also heen 
derived from bile. They are bilifuscin, C'^'H-'^N'O*, biliprp^in, 

C,o_[£r2^>^.(jH^ and bilihumin. 

CREATINE. 

C*H9N302 + H20 

This body was discovered by Chevreul in meat broth. It 
exists ready formed in the muscles, and jjasses into the extract 
of meat. It may be prepared by treating the solution of this 
extract with basic acetate of lead, filtering, freeing the filtrate 
from excess of lead by hydrogen sulphide, and evaporating the 
solution at a gentle heat until it crystallizes. The crystals are 
separated from the mother-liquor, and alcohol added to the 
latter precipitates a fresh quantity of creatine (Neubauer.) 

Creatine crystallizes in brilliant, colorless, oblique rhombic 
prisms, containing one molecule of water, which they lose at 
100°, J3ecoming opaque. 

By the action of acids or by long boiling with water, crea- 
tine is converted into creatuiine. 

Creatine. Creatiniue. 

When creatine is boiled with baryta-water, it is converted 
into sarcosinc, ammonia being disengaged and barium carbon- 
ate precipitated at the same time. It is generally considered 
that the ammonia and carbon dioxide are produced in this case 
at the expense of urea, which is formed directly by the decom- 
position of creatine. 

C^H^'N^O' _|_ ii^O ^ C'H^NO' + CH*N^O 

Creatine. Sarcosine. Urea. 

Sarcosine is methylglycocol. It is isomeric with lactamide 
and alanine. It may be obtained artificially by treating mono- 
chloracetic acid with methylamine (A^olhard.) 

C2H2C10.0H + CH3.NH2 = C2H20<^^(C^"') + IICl 

Monochloracetic add. Metliylamine. Sarcosine. 

Volhard has made the synthesis of creatine by the action of 
cyanamide on sarcosine. Cyanamide, CN.NH"-, represents am- 
monium cyanate less the elements of water. 

CN'IP + C'H^NO- == C^IPN'O- 

Cyanamide. Sarcosine. Creatine. 



CREATININE. 67." 



i.) 



CREATININE. 

This body exists in uniscular tissue independently of creatine. 
It may be precipitated from the mother-liquor from which the 
latter body has deposited, by adding an alcoholic solution of 
zinc chloride, which forhis a crystalline combination with the 
creatinine. 

Creatinine crystallizes in oblique rhombic prisms. It is much 
more soluble in alcohol than creatine. It has basic properties, 
and forms a crystallizable compound with hydrochloric acid. 

Creatine and creatinine have been found not only in the 
muscles, but in small quantities in the brain, blood, and urine. 



Among the products of disassimilation we may also mention : 

Leucuie, C^H^'^NO', which belongs to the homologous series 
of glycocol, and is found in many organs, especially in the 
pancreas, the salivary glands, the spleen, and the liver (page 
546). 

Tyrosine^ C^H^^NO^, a body crystallizing in fine needles 
may be obtained from the pancreas and the spleen (page 631). 

It is known also that leucine and tyrosine may be obtained 
directly by the action of alkalies upon complex nitrogenized 
matters (page 661). 

Hippuric acid, C^H^NO^, the origin of which has already 
been indicated (page 627). 

Uric acid, C^H*N*0^ which exists in small quantity in 
human urine, and which constitutes a large proportion of the 
urine of birds and reptiles (page 559). 

AUantoin, C*H'^N*0^, a product of the oxidation of uric acid, 
which A^auquelin and Buniva formerly extracted from the am- 
niotic liquor of the cow, and which has also been found in the 
urine of young calves (page 563). 

Various other products are related to uric acid. They are : 

Xanthine, C^H^N^O'^, a yellow matter, which Proust discov- 
ered in certain rare calculi (xanthic calculi), and which has 
also been found in small quantity in the muscles, pancreas, liver, 
and urine. 

57* 



G7G ELEMENTS OF MODERN CHEMISTRY. 

Iltjpoxnnthine or sarcine, C^H^N'O, a white, amorphous sub- 
stance which Scherer obtained from the spleen, and of which 
Strecker lias noticed the existence in muscular tissue. Hypo- 
xanthine forms a crystallizal)le combination with hydrochloric 
acid. It presents interesting relations of composition with xan- 
thine and uric acid. 

Uric acid CSH^N^QS 

Xanthine C^UiN^Oz 

Hypoxanthine C5HiN*0 

When hypoxanthine is boiled with nitric acid, it is converted 
into a nitrogenized body. By the action of reducing agents, 
such as ferrous sulphate, this nitrogenized body is converted 
into giKinine^ C^H^N^O. The latter body was first obtained 
from guano. It has been found in the tissue of the pancreas. 



MEASURES OF WEIGHT. 



1 Milligramme 
1 Centigramme 
1 Decigramme 
1 Gramme 
] Deeagramme 
1 Hectogramme 
1 Kilofjramme 



GRAINS. 

0.01543 

0.15432 

1.54323 

15.43234 

154.32349 

1543.234SS 

15432.34880 



OVNTES TROY 
= 480 Ci RAINS. 

0.000032 
0.000321 
0.003215 
0.032150 
0.321507 
3.215072 
32.15072G 



POUNDS 
ATOUtDl'POIS. 

0.0U00022 
0.0000220 
0.0002204 
0.0022046 
0.0220402 
0.2204(;2l 
2.2046212 



1 Grain = 0.064799 grammes. 

1 Oz. Troy = 31.103496 

1 Lb. Avoirdupois = 0.453495 kilogrammes. 

1 Cubic Centimetre of water weighs 1 srramme. 



To convert Centigrade degrees into Fahrenheit degrees, multiply by 9 and 
divide by 5 ; add 32°. 

To convert Fahrenheit degrees into Centigrade degrees, subtract 32°, then 
multiply by 5 and divide by 9. 



1 Metre ^ 39.370708 inches. 

1 Centimetre = 0.39370 " 
1 Millimetre = 0.03937 " 



1 Inch 



= 2.539954 centimetres. 



57* 



677 



INDEX. 



Acetamido, 506. 
Acetates, 495. 
Acetic anhydride, 499. 
Acetone, 503. 
Acetones, 420. 
Acetonitrile, 449. 
Acetyl chloride, 502. 
Acetylene, 520. 
Acid', 42. 

acetic, 492. 

aconitic, 559. 

acrylic, 512. 

alloxanic, 561. 

aniidacetic, 544. 

/3-aniidopropionic, 546. 

anisic, 631. 

anthranilic, 634. 

autimonic, 1S9. 

arsenic, 182. 

arsenious, 179. 

aspartic, 554. 

benzoic, 626. 

boric, 193. 

bromic, 130. 

butyric, 508. 

campholic, 601. 

camphoric, 602. 

cai)roic, 510. 

carbonic, 206, 209. 

cerotic, 511. 

chlorethylsulphurous, 528. 

chloric, 125. 

chlorous, 123. 

cholalic, 672. 

chromic, 347. 

cinchonic, 654. 

citraconic, 559. 

citric, 558. 

crotonic, 512. 

cyanic, 438. 

cyan uric, 442. 

dialuric, 562. 

dibromosuccinic, 551. 

digallic, 590. 



Acid, elaidic, 512. 

cthylnitrolic, 467. 
ethylphosphinic, 485. 
' ethylsulphuric, 468. 
formic, 490. 
fumaric, 553. 
gallic, 632. 
gluconic, 570. 
glutamic, 659. 
glyceric, 543. 
glycocholic, 672. 
glycollic, 537. 
glyoxylic, 538. 
hipituric, 627. 
hydracrylic, 543. 
hydriodic, 132. 
hydrobromic, 128. 
hydrochloric, 116. 
hydrocyanic, 431. 
hydrofluoric, 136. 
hydrofluo^^ilicic, 198. 
hydrosulphurous, 100. 
hypobromous, 129. 
hypochlorous, 122. 
hypophosphorous, 171. 
hypoi!^ulphuric, 109. 
hypo?ul]>hurous, 109. 
iodic, 134. 
iodo])i'opionic, 508. 
isethionic, 528. 
isobutyric, 509. 
isophthalic, 638. 
itaconic, 559. 
lactic, 539. 
leucic, 546. 
maleic, 553. 
malic, 552. 
malonic, 536. 
manganic, 343. 
margaric, 511. 
meconic, 646. 
mellic, 593. 
mesoxalic, 561. 
metaphosphoric, 175. 
679 



G80 



ELEMENTS OF MODERN CHEMISTRY. 



Acid, nicthylnitrolic, 451. 
monobroiuosuccinic, 551. 
monochloracctic, 498. 
nitric, 157. 

nitrohydrochloric, IGO, 
oleic, 512. 
opianic, 650. 
oxalic, 547. 
oxamic, 550. 
oxybcnzoic, 631. 
palmitic, 511. 
parabanic, 562. 
paralactic, 539, 541. 
paratartaric, 558. 
paroxybenzoic, 631. 
penfathionic, 97. 
perbromic, 130. 
perchloric, 125. 
perchromic, 87. 
periodic, 135. 
permanganic, 344. 
persulphuric, 111), 
phosphoric, 173. 
phosphorous, 172. 
phthalic, 637. 
picraiiiic, 607. 
picric, 607. 
propionic, 507. 
purpuric, 563. 
pyrogallic, 633. 
pyrophosphoric, 174. 
pyrotartaric, 555. 
pyruvic, 555. 
quinic, 651. 
quiuolic, 653. 
ruberythric, 642. 
salicylic, 629. 
silicic, 199. 
stannic, 354. 
stearic, 511. 
succinic, 550. 
sulphocarbonic, 215. 
sulphosulphuric, 109. 
sulphuric, l02. 

" faming, 108. 

sulphurous, 97. 
tannic, 589. 
tartaric, 554. 
tartronie, 556. 
taurocholic, 672. 
.terephthalic, 638. 
tetrathionic, 97. 
trichloracetic, 499. 
trithionic, 97. 
uric, 559, 675. 



Acid, valeric, 510. 
Acids, diatomic, 428. 

fatty, 488, 505. 

monatomic, 418. 

polyatomic, 536. 
Aconitino, 655. 
Acrolein, 512. 
Affinity, 11. 
Air, 03. 
Alanine, 545. 
Albumen, 660. 
Albuminoid matters, 657. 
Alcohol radicals, 425. 
Alcohol, allyl, 478. 

amyl, 475. 

benzyl, 623. 

butyl, 474. 

cetyl, 477. 

ethyl, 455. 

hei)tyl, 477. 

hexyl, 477. 

methyl, 447. 

octyl, 477. 

propyl, 474. 
Alcohols, diatomic, 427, 521. 

monatomic, 417, 444, 472. 

polyatomic, 429, 561. 

primary, secondary, tertiary, 
472. 
Aldehj^de, acetic, 505. 

anisic, 631. 

benzoic, 624. 

butyric, 509. 

crotonie, 512. 

formic, 492. 

salicvlic, 628. 
Aldehvdcs, 420. 
Aldol, 501. 
Alizarin, 041. 
Alkaloids, 643. 
Allantoin, 563. 
Alloxan, 561, 
Alloxantin, 562. 
Alloys, 236. 
Allyl alcohol, 478. 

bromide, 518. 

iodide, 478. 

sulphide, 478. 

sulphocyanate, 478. 
Alum, 315. 
Aluminium, 313. 

chloride, 314. 

oxide, 314. 

silicates, 317. 

sulphate, 315. 



INDEX. 



G81 



Amalgams, 236. 
Amides, 421. 
Aminos, 422, 479. 
Ammonia, 13U. 

action of CI and I, 14.3. 
action of potassium, 145. 
Ammonium amalgam, 145. 
carbonate, 14t». 
chloride, 146. 
cyanatc, 440. 
formate, 491. 
nitrate, 148. 
oxalate, 549. 
sulphate, 149. 
sul}>hidc, 147. 
sulphocyanate, 444. 
sulphydrate, 147. 
theory of, 146. 
Amygdalin, 587. 
Amyl alcohols, 475. 
chloride, 476. 
iodide, 476. 
oxide, 476. 
Amylenes, 519. 

bromides, 520. 
Anilides, 609. 
Aniline, 608. 
colors, 613. 
salts, 608. 
Anisic compounds, 631. 
Anthracene, 640. 
Anthracite, 202. 
Anthraquinone, 641. 
Antimonio-potassium tartrate, 557. 
Antimony, 185. 

antimonate, 188. 
oxide, 188. 
pentachloride, 187. 
pentasulphide, 190. 
pentoxide, 189. 
trichloride, 186. 
trisulphide, 189. 
Apomorphine, 648. 
Aromatic compounds, 590. 
Arsenic, 176. 

chloride, 179. 
disulphide, 183. 
pentasulphide, 184. 
pentoxide, 182. 
trioxide, 179, 
trisulphide, 183. 
Arsines, 423. 
Asparagin, 553. 
Atomic heats, 34. 
Atomic theory, 27. 
2d^ 



Atomicity, theory of, 222. 
Atropine, 650. 
Aurin. 608. 
Australinc, 598. 
Azobenzol, 604. 
Azoxybenzol, 604 

Barium, 302. 

carbonate, 304. 
chloride, 303. 
dioxide, 302. 
nitrate, 303. 
oxide, 302. 
sulphate, 304. 
sulphide, 303. 
tests, 304. 
Beer, 579. 
Benzamide, 627. 
Benzol, 602. 

monobromo-, 603. 

monochloro-, 603. 

Benzoyl hydride, 624. 

chloride, 625. 
Benzyl alcohol, 623. 
aldehyde, 024. 
chloride, 020. 
Bcnzylamine, 624. 
Berthollet's laws, 265. 
Bilirubin, 673. 
Biliverdin, 673. 
Bismuth, 349. 

chloride, 350. 
nitrate, 351. 
oxide, 350. 
tests, 351. 
Bituminous coal, 202. 
Borneol, 602. 
Boron, 191. 

chloride, 192. 
fluoride, 193. 
oxide, 193. 
Boro-potassium tartrate, 558. 
Bromine, 127. 
Brucine, 654. 
Bunsen burner, 221. 
Butane, 455. 
Butyl alcohols, 474. 
Butylenes, 518. 
Butyral, 509. 
Butyrone, 509. 

Cacodyl, 453. 
Cadmium, 337. 

iodide, 3.37. 

oxide, 337. 



682 



ELExMENTS OF MODERN CHEMISTRY. 



Cadmium, sulphate, 338. 

sulphide, 337. 
Cicsium, 300. 
Catfcine, 057. 
Calcium, 305. 

carbonate, 307. 

chloride, 307. 

hydrate, 305. 

hypochlorite, 309. 

lactate, 542. 

nitrate, 307. 

oxide, 305. 

sulphate, 308. 

tests, 310. 
Camphenes, 599. 
Camphor, 600. 

artificial, 591). 
Carbamide, 440. 
Carbon, 200. 

dioxide, 209. 

disulphide, 215. 

estimation of, 406. 

monoxide, 207. 

compounds of, 438. 

oxysulphide, 216. 

tetrachoride, 449. 

sesquichloride, 516. 
Carbonates, 275. 
Carbonyl chloride, 208. 
Carbylamincs, 450, 465. 
Casein, 667. 
Cellulose, 584. 
Charcoal, 202. 

absorbent properties of, 204. 
Chloral, 502. 
Chlorides, 246. 

monatomic, 415. 

of acid radicals, 421. 
Chlorine, 112. 

and Br and I, analogies, 130. 

peroxide, 124. 
Chloroform, 448. 
Chlorotoluols, 620. 
Chlorous anhydride, 123. 
Cholesterin, 671. 
Chondrin, 668. 
Chromatcs, 347. 
Chromium, 346. 

chlorides, 348. 

oxides, 346. 
Cinchona bark, 650. 
Cinchonine, 653. 
Citrine, 000. 
Cobalt, 338. 

chloride, 339. 



Cobalt, oxides, 338. 

sulphate, 339. 

tests, 339. 
Cocaine, 655. 
Codeine, 648. 

Combination, laws of, 23-27. 
Combustion, 58. 
Conine, 644. 
Copper, 368. 

acetates, 496. 

alloys, 375. 

carbonates, 374. 

chlorides, 372. 

oxides, 371. 

sulphates, 373. 

sulphides, 372. 

tests, 375. 
Cotarnine, 650. 
Creatine, 074. 
Creatinine, 075. 
Cresols, 021. 
Cupellation, 359, 389. 
Cyanobenzol, 005. 
Cyanogen, 430. 

bromide, 437. 

chlorides, 436. 

iodide, 437. 
Cymene, 599. 

Dextrin, 581. 
Diamines, 428. 
Diamond, 201. 
Diazoamidobenzol, 612. 
Diazobenzol compounds, 610. 
Dichlorhydrin, 531. 
Dimethylarsine, 453. 
Dioxindol, 030. 
Diphenylamine, 014. 
Diphenylketonc, 027. 
Ductility, 233. 
Dulcite, 500. 

Elementary analysis, 406. 
Elements, table of, 39. 
Emulsin, 587. 
Epichlorhydrin, 531. 
Erythrite, 505. 
Ethane, 455. 
Ether, 459. 

acetylacetic, 498. 

Kay's, 449. 
Ethers compound, 419. 

simple, 454. 
Ethyl acetate, 497. 

carbamate, 470. 



INDEX. 



G83 



Ethyl carbonate, 469. 

carbylamine, 405. 

chloride, 4Go. 

chlorocarbonatc, 470. 

cyanate, 46S. 

cyaniJe, 4(55. 

hydrate, 455. 

iodide, 464. 

nitrate, 467. 

nitrite, 466. 

oxalate, 549. 

oxide, 459. 

sulphate, 469. 

sulphide, 463. 

sulphydrate, 462. 
Ethylaiuines, 482. 
Ethylene, 513. 

acetates, 525. 

bromide, 515. 

chlorhydrate, 524. 

chloride, 515. 

chloro-derivatives, 615. 

diamines, 527. 

hydrate, 523. 

iodide, 515. 

nitrates, 525. 

oxide, 525. 

bases from, 526. 
Ethylhydrazine, 480. 
Ethylidene chloride, 501, 516. 
Ethylphosphines, 483. 

Fats, natural, 532. 
Fermentation, 576. 
Ferric chloride, 327. 

oxide, 326. 

sulphate, 329. 
Ferro-Yjotassium tartrate, 567. 
Ferrous chloride, 327. 

lactate, 542. 

oxide, 325. 

sulphate, 328. 
Fibrin, 662. 
Flame, 218. 
Fluorescein,^638. 
Fluorine, 136, 
Formates, 491. 
Formonitrile. 432. 
Formulae, constitutional, empirical, 

rational, 419. 
Fulminates, 452. 
Functions, organic, 414. 

Gallium, 335. 
Gay-Lussac's law, 27. 



Gelatin, 667. 
Gilding, 394. 
Globulin, 667. 
Glucosan, 568. 
Glucose, 567. 
Glucosides, 586. 
Glycerin, 529. 

ethers of, 630. 
Glycocol, 544. 
Glycogen, 583. 
Glycol, 523. 

ethers of, 427. 
Glycols, 427, 521. 
Glyoxai, 538. 
Gold, 391. 

assay, 395. 

chlorides, 393. 

oxides, 393. 
Graphite, 201. ' 
Guanine, 676. 
Gum arabic, 584. 

tragacanth, 584. 
Gums, 583. 
Gun-cotton, 586. 

Hematin, 666. 
Hemoglobin, 664. 
Hexamethylbenzol, 619. 
Homologous bodies, 405. 
Hydrazine, 480. 
Hydrazobenzol, 604. 
Hydrocarbons, C»H'^n+2, 415, 470. 

CnlF", 517. 

C»H^"-2, 520. 
Hydrogen, 48. 

absorption by palladium, 61. 

antimonide, 186. 

arsenide, 178. 

dioxide, 85. 

estimation of, 406. 

persulphide, 96. 

phosphide, 105. 

silicide, 195. 

sulphide, 92. 
Hj'droquinone, 616. 
Hydroxylamine, 149. 
Hypochlorous anhydride, 122. 
Hypoxanthine, 676. 

Indigo, 633. 

white, 634. 
Indium, 336. 
Indol, 636. 
Inosite, 571. 
luulin, 583. 



684 



ELEMENTS OF MODERN CHEMISTRY. 



Iodine. 1:^0. 

oxides, 131. 
Iron. IMS. 

carbonate, 329. 

cast, 328. 

chlorides, 327. 

lactate, 542. 

oxides, 325. 

soft, 322. 

sulphates, 328. 

sulphides, 327. 

tests, 330. 
Isatin, 635. 
Isomerism, 412. 
Isomorphism, 37, 255. 
Isopropyl iodide, 474. 
Isoturpentine, 600. 

Kay's ether, 449. 

Laetamidc, 542. 
Lactates, 542. 
Lactose, 574. 
Lamp-black, 203. 
Lead, 357. 

acetates, 496. 

carbonate, 366. 

chloride, 364. 

chromate, 367. 

dioxide, 362. 

iodide, 364. 

monoxide, 361. 

nitrate, 365. 

red oxide, 362. 

sulphate, 365. 

sulphide, 363. 

tests, 367. 
Lecithine, 670. 
Leucanilines, 612. 
Leucine, 546, 675. 
Levulosan, 570. 
Levulose, 570. 
Lignite, 202. 
Lime, 305. 
Lithium, 299. 

Magnesium, 310. 

carbonate, 312. 

citrate, 559. 

chloride, 311. 

oxide, 311. 

sulphate, 312. 

tests. 313. 
^rallcability, 233. 
Maltose, 575. 



Manganese, 342. 

carbonate, 345. 

dioxide, 342. 

oxides, 342. 

sulphate, 344. 

tests, 345. 
Mannitan, 566. 
Mannite, 566. 
Marsh's apparatus, ISl. 
Marsh gas, 445. 
Matches, 165. 
Mercur-ethyl, 4S6. 
Mercuric chloride, 3S0. 

iodide, 381. 
Merour-niethyl, 486. 
Mercurous chloride, 379. 

iodide, 381. 
Mercury, 375. 

cyanide, 433. 

fulminate, 452. 

nitrates, 382. 

oxides, 378. 

sulphates, 383. 

sulphide, 378. 

tests, 383. 
Mesitj-^lcne, 505. 
JMetaldehyde, 501. 
Metallic carbonates, 275. 

chlorides, 246. 

hydrates, 244. 

nitrates. 27 1 . 

oxides, 238. 

sulphates, 273. 

sulphides, 245. 
Metals, classitication of, 277. 

general properties of, 231. 
Metamerism, 412. 
Methane, 445. 
Mcthylamines, 481. 
Mcthylbcnzol, 618. 
Methyl bromide, 448. 

chloride, 448. 

compounds, 445. 

cyanide, 4-19. 

hydrate, 447. 

iodide, 448. 

nitrate, 450. 

nitrite, 450. 

oxide, 447. 

salicylate. 630. 
Mineral waters, 82. 
Minium, 362. 
Molecular weights, determination 

of, 410. 
Monobromobonzol, 603. 



INDEX. 



685 



Monoohlnrobcnzol, nO:?. 
Monot'hlorliydrin, b'M. 
Morphine, 1)47. 
Murexiile, 503. 
Myosin, 663. 

Naphthalene, 6311. 
Naphthol, 640. 
Naphthyhxniiue, C40. 
Nareeinc, 646. 
Narcotine, 649. 
Neurinc, 527, 671. 
Nickel, 340. 

chloride, 341. 

oxides, 340. 

sulphate, 341. 

tests, 341. 
Nicotine, 645. 
Nitrates, 271. 
Nitrethane, 466. 
Nitric anhydride, 157. 
Nitrobenzol, 604. 
Nitroferrocyanides, 436. 
Nitrogen, 138. 

chloride, 144. 

dioxide, 153. 

estimation of. 406. 

group, gen. considerations, 190. 

iodide, 145. 

monoxide, 151. 

pentoxide, 157. 

peroxide, 155. 

trioxide, 154. 
Nitroglycerin, 530. 
Nitromethane, 450. 
Nitrosyl chloride, 161. 
Nitrotoluols, 620. 
Nitryl, chloride and bromide, 156. 
Nomenclature, 37. 
Nornarcotine, 650. 
Notation, 37. 

Oils, essential, 506. 

fatty and drying, 533. 
Olein, 533. 
Opium, 646. 
Orcin, 486, 621. 

Organo-metallic compounds, 423. 
Orpiuient, 183. 
Oxalates, 548. 
Oxamide, 549. 
Oxindol, 636. 
Oxygen, 54. 
Oxyphenols, 614. 
Ozone, 59. 



Pahnitinc, 5:?3. 
Papaverine, 646. 
Paraeoniue, 645. 
Paraldehyde, 501. 
Porsulphuric oxiile, 110. 
Phcnanthrene, 641. 
Phenol, 605. 
Phloretin, 589. 
Phloridzin, 588. 
Phloroglucin, 589, 618. 
Phosphincs, 423. 
Phosphoric anhydride, 173. 
Phosidiorus, 1()1. 
bromide, 169. 
iodide, 170. 
oxyehloridc, 169. 
pcntaehloride, 168. 
pentoxide, 173. 
sulphides, 176. 
sulphochloridc, 159. 
trichloride, 168. 
Pinacolin, 505. 
Pinaconc, 522. 
Platinum, 395. 

chlorides, 397. 
Plumbago, 201. 
Polymerism, 412. 
Pupulin, 588. 
Potassamide, 145. 
Potassium, 282. 

acetate, 495. 

acid- sulphate, 288. 

bromide, 286. 

carbonates, 289. 

chlorate, 288. 

chloride, 285. 

chromate, 347. 

cyanate, 439. 

cyanide, 433. 

dichromate. 847. 

ferricyanide, 435. 

fcrroc3'anidc, 434. 

hydnitc, 283. 

iodide, 285. 

methylate, 447. 

nitrate, 286. 

oxalates, 549. 

oxides, 283. 

pcrchlorate, 289. 

permanganate, 344. 

sulphate. 288. 

sulphides, 284. 

sulphocyanatc, 444. 

tartrates, 556. 

tests, 290. 



58 



686 



ELEMENTS OF MODERN CliEMISTRY. 



Pottery, 317. 
Propionitrile, 465. 
Propyl alcohols, 474. 

glycols, 529. 

iodide, 474. 
Propylene, 518. 
Prussian blue, 435. 
Pscudomorphine, C17. 
Purpurin, 643. 
Pyrocatechin, 615. 
Pyrogallol, 618. 

Quinine, 651. 
Quinone, 616. 

Radicals, monatomic, 425. 

polyatomic, 426. 
Realgar, 183. 
Resorcin, 615. 
Respiration, 669. 
Richter's laws, 253. 
Rochelle salt, 556. 
Rosaniline, 611. 
Rubidium, 300. 

Saccharose, 571. 
Safety-lamp, 219. 
Salicin, 588. 
Salicyl hydride, 628. 
Saligenin, 588, 628. 
Salts, 43, 250. 

action of acids, 265. 
bases, 267. 
electricity, 262. 
heat, 261. 
metals, 264. 
salts, 268, 270. 
water, 256. 

neutral, acid, and basic, 252. 
Saponification, 535. 
Sarcine, 676. 
Sarcosine, 674. 
Selenium, 111. 
Silica, 199. 
Silicon, 194. 

chloride, 196. 

fluoride, 197. 

oxide, 199. 
Silver, 384. 

acetate, 497. 

assay, 389. 

chloride, 387. 

fulminate, 452. 

fulminating, 387. 

iodide, 388. 



Silver, nitrate, 388. 

oxide, 387. 

sulphide, 387. 

tests, 389. 
Silvering, 389. 
Soap, 534. 
Sodium, 291. 

acetate, 496. 

acid-carbonate, 298. 

acid-sulphate, 295. 

borate, 298. 

carbonate, 295. 

chloride, 293. 

hydrate, 292. 

hydrosulphite, 100, 

hyposulphite, 109. 

nitroferrocyanide, 436. 

oxides, 292. 

phosphates, 298. 

sulphate, 294. 

sulphide, 292. 

tests, 299. 
Sorbin, 571. 
Sorbite, 567. 
Specific heat, 34. 
Spectrum analysis, 300. 
Stannethyls, 487. 
Starch, 580. 
Stearin, 533. 
Stearin candles, 534. 
Steel, 323. 
Stibines, 423. 
Strontium, 304. 
Strychnine, 654. 
Succinic anhydride, 551. 
Succinyl chloride, 551. 
Sugar, cane, 571. 

grape, 567. 

inverted, 574. 

milk, 574. 
Sugars, 567. 
Sulphates, 273. 
Sulphur, 88. 

chlorides, 126. 

soft, 90. 
Sulphuric anhydride, 101. 
Sulphurous anhydride, 97. 
Sulphuryl chloride, 100, 106. 
Supersaturation, 259. 
Syntonin, 064. 

Tannin, 589. 
Tartar-emetic, 557. 
Tartrates, 556. 
Taurine, 528. 



INDEX. 



087 



Tellunum, 111. 
Tercbene, 599. 
Tcrpilene, 600. 
Torpin, 598. 
Tctrachloiethylenc, 516. 
Tetramethylammonium, 482. 
Tetiethvlainmoiiium, 483. 
ThiiUiiuu, ;!U2. 
Thebiiine, 046. 
Theine, 657. 
Theobromine, 656. 
Tin, 352. 

dichloride, 355. 

oxides, 354. 

sulphides, 355. 

tests, 357. 

tetrachloride, 356. 
Toluidines, 622. 
Toluol, 618. 
Tribenzylamine, 624. 
Trichlorhydrin, 532. 
Triethylatnine, 483. 
Trimethylamine, 482. 
Trimethylcarbinol, 475. 
Trinitrophenol, 607. 
Turpentine, 596, 598. 
Tyrosine, 631. 

Urea, 440. 

Ureas, compound, 443. 



Urethane, 470. 

Verdigris, 497. 
Vermillion, 379. 
Vinegar, 494. 

Water, 70. 

analysis, 71. 

mineral, 82. 

natural state, 79. 

synthesis, 72. 
Wax, 477. 
Wine, 578. 
Wood-spirit, 447. 

Xanthine, 675. 

Xyloidiu, 582. 
Xylols, 637. 

Yeast, 676. 

Zinc, 330. 

chloride, 333. 

hydracrylate, 543. 

lactate, 542. 

oxide, 332. 

sulphate, 333, 

sulphide, 333. 

tests, 334. 
Zinc-ethyl, 486. 



THE END. 



PUBLICATIOXS OF J. B. L1PPL\C0TT ^ CO. 



NOW COMPLETE, IN FIFTEEN VOLUMES. 



THE 



J^EW 8TAKDARB EBLTIOK 



PRESCOTT^S^A^ORKS 

WITH THE 

Anthor's Latest Corrections and Additions. 

EDITED BY 



AS FOLLOWS : 

HISTORY OF FERDINAND AND ISABELLA, 

3 Volumes. 

HISTORY OF THE CONQUEST OF MEXICO, 

3 Volumes. 

HISTORY OF THE CONQUEST OF PERU, 

2 Volumes. 

HISTORY OF THE REIGN OF PHILIP II., 

3 Volumes, 

HISTORY OF THE REIGN OF CHARLES V., 

3 Volumes. 

PRESCOTT'S MISCELLANEOUS ESSAYS^ 

1 Volume. 



Thi3 tCdition is Illustrated with Maps, Plates, and Engravings 

Price per volume, i2mo, in fine English cloth, with black 

and gold ornamentation, $2.00; library sheep, 

$2.50; half calf, gilt back, $3.50. 



"It would be difficult to point out 
anion.i: any works of living historians 
the equal of those which have pro- 
ceeded from Mr. Prescott's pen." — 
Harper's Magazine. 

" We would gladly do our share to- 
wards making acknowledgment of the 
debt of gratitude we all owe to Messrs'. 
l.ippincott & Co. for the superb and 
even monumental edition of the IVo^ks 
of William H. Prcscott, whicli ihey 



have at last brought to completion." — 
Ne7v York Christian Union. 

" The typography, indeed the entire 
mechanical execution, of these books 
is exquisite; and we imhcsitatingly 
pronounce the series not only the bcsi 
edition of Prescott's Works ever pul)- 
lished, but one of the handsomest sol 
of books the American press has given 
us." — Boston Journal. 



FUBLICATIONS OF J. B. LIPPINCOTT &- CO. 



il CL 



EDITED BY 



REV. W. LUCAS COLLINS. 

20 Volumes. Small lamo. Fine Cloth, $i.oo each. The 

20 Volumes, in neat Cloth Box, $20.00. Complete 

in 10 Volumes, in neat Cloth Box, $15.00. 



NOW COMPLETE, EMBRACING 



7. HOMER'S ILIAD. 

2. HOMER'S ODYSSEY. 

3. HERODOTUS. 

4. G/ESAR. 

5. VIRGIL 

6. HORAGE. 

7. /ESGHYLUS. 

8. XENOPHON. 

9. GIGERO. 

W. SOPHOGLES. 



11. PLINY. 

12. EURIPIDES. 

13. JUVENAL. 

14. ARISTOPHANES. 

15. HESIOD d THEOGNIS. 

16. PLAUTUS & TERENGE. 

17. TAGITUS. 
IS, LUGIAN. 

19. PLATO. 

20. GREEK ANTHOLOGY. 



The aim of lliis delij^htful series of books is to explain, suffi- 
ciently for general readers, who these great writers were, and what 
they wrote; to give, wherever possible, some connected outline 
of ihe story which they tell, or the facts which they record, checked 
by the results of modern investigations ; to present some of their 
most striking passages in approved English translations, and to 
illustrate them generally from modern writers; to serve, in short, 
as a popular retrospect of the chief literature of Greece and Rome. 



" Each successive issue only adds to 
our appreciation of the learning and 
skill with which this admirable enter- 
prise of bringing the best classics within 
easy reach of English readers is con- 
ducted." — N'g:u York Independent. 



" There is not a volume of this most 
admirable and useful series that is not 
done in a very masterly manner, ami 
worthy of the highest praise." — British 
Quarterly Review. 



*:f!* A Supplemental Series in the same size and type is being 
issued. It will not he extended beyond eight or ten volumes 



PUBLICATIONS OJ- y. B. LirPINCOTl ^ CO. 



VALUABLE WORKS OF REFERENCE. 



Lipplncott's Pronouncing Biographical Dictionary. 

Containing complete and concise Biographical Sketches of the 
Eminent Persons of all Ages and Countries. By J. Thomas, 
A.M., M.D. Imperial 8vo. Sheep, ;?i5.oo. 2 vols. Cloth. 
$22.00. 

Allibone's Critical Dictionary of Authors. 

A Dictionary of English Literature and British and American 
Authors, Living and Deceased. By S. Austin Allibonk, LL.D. 
3 vols. Imperial Svo. Extra cloth. $22,50. 

Lipplncott's Pronouncing Gazetteer of the World. 

A Complete Geographical Dictionary. By J. Thomas and 
T. B\LDWIN. Royal Svo. Sheep. $10.00. 

Allibone's Dictionary of Prose Quotations. 

By vS. Austin Allibone, LL.D. With Indexes. Svo. Extra 
cloth. $5.00. 

Allibone's Dictionary of Poetical Quotations. 

By S. Austin Allibonp, LL.D. With Indexes. Svo. Extra 
cloth. $5.00. 

Chambers's Encyclopaedia. 

American Bevised Edition. 
A Dictionary of Useful Knowledge. Profusely Illustrated with 
M.ips, Plates, and Woodcuts. 10 vols. Royal Svo. 

Chambers's Book of Days. 

A Miscellany of Popular Antiquities connected with the Cal- 
endar. Profusely Illustrated. 2 vols. Svo. Extra cloth. $8.00. 

Dictionary of Quotations, 

From the Greek, Latin, and Modern Languages. With an 
Index. Crown Svo. Extra cloth. $2.00. 

Furness's Concordance to Shakespeare's Poems. 

An Index to Every Word therein contained, Avith the Complete 
Poems of Shakespeare. Svo. Extra cloth. $4.00. 

Lempriere's Classical Dictionary. 

Containing all the Principal Names and Terms relating to 
Antiquity and the Ancients, with a Chronological Table. Svo. 
Sheep. ^3.75. i6mo. Cloth. $1.50. 



>Ky=' The above Works are also bound in a variety of handsome extra styles 



PUBLICATIONS OF J. B. LIPPLVCOTT ^ CO. 

CLASSICAL W ORKS OF REFEHEHCE. 

GARDNER'S LATIN LEXICON. 

A Dictionary of the Latin Language, particularly adapted to the 
Classics usually studied preparatory to a Collegiate Course. By 
Francis Gardner, A.M. 8vo. Sheep. $3.00. 

LEVERETT'S LATIN LEXICON. 

A Copious Lexicon of the Latin Language. Compiled chiefly from 
the Magnum Totius Latinitatis Lexicon of Facciolati and For- 
cellini, and the German Works of Scheller and Luenemann, 
embracing the Classical Distinctions of Words, and the Etymo- 
logical Index of Freund's Lexicon. By F. P. Leverett. Large 
8vo. Sheep. $5.50.* 

This work contains all the words in the Latin language, embracing those used 
by authors of the classical, ante-classical, and post-classical periods, with words 
jf modern origin coined for scientific and other purposes. 

LEMPRIERE'S CLASSICAL DICTIONARY. 

Containing a full account of all the Proper Names mentioned in 
ancient authors, with Tables of Coins, Weights, and Measures 
in use among the Greeks and Romans ; to which is prefixed a 
Chronological Table. 8vo. Sheep. $3.25.* Abridged Edi- 
tion. i2mo. Extra cloth. ^1.50. 

The original text of Lempriere has in this edition been carefully revised and 
amended, and much valuable original niatter added. The work is now a complete 
Bibliotheca Classica, containing in a condensed and readily accessible form all the 
information required by the student upon the geography, topography, history, lit- 
eratuie, and mythology of antiquity and of the ancients, with bibliographical ref- 
etences for such as wish to get hiUer information on the subjects treated of. 

GROVES'S GREEK DICTIONARY. 

A Greek and English Dictionary', comprising all the Words in the 
writings of the most popular Greek authors, with the difficult 
inflections in them, and in the Septuagint and New Testament. 
Designed for the Use of Schools and the Under-Graduate Course 
of a Collegiate Education. By John Groves. With correc- 
tions and additional matter by " the American editor. Svo. 
Sheep. $2.25.* 

The object of the compiler has been to produce a work which young Greek 
scholars could use with ease and advantage to themselves, but sufficiently full to 
be equally serviceable as they advanced. 

PICKERING'S GREEK LEXICON. 

A Comprehensive Lexicon of the Greek Language, adapted to the 
Use of Colleges and Schools of the United States. By John 
Pickering, LL.D. New Edition, revised and corrected. Large 
Svo. Sheep. ^5.50.-^ 
This work contains all the words in the Greek language, with their correct inter- 
pretation into English, and their different shades of meaning carefully distinguished 
and illustrated by citations from standard authors. 



PUBLICATIONS OF J. B. LIPPINCOTT ^ CO. 



THE AMERICAN REVISED EDITION OF 

CHAMBERS'S ENCYCLOP/EDIA, 

A DICTIONARY OF UNIVERSAL KNOWLEDGE FOR THE PEOPLE. 

Illustrated with numerous Wood Engravings, Plates, and Maps. 

In ten volumes, Royal Octavo. 

THREE EDITIONS OF THIS VALUABLE WORK ARE PUBLISHED: 
THE REVISED TRADE EDITION. 

Embracing the complete text, and 4000 text illustrations. 

THE REVISED POPULAR EDITION. 

Same as above, printed on finer paper ; with 40 handsome maps. 

THE AMERICAN REVISED EDITION. 

Including maps and 80 full-page plates. 

Each edition bound in various stylesi Prices ranging from $22,50 upwards. 

This great work is complete in TEN ROYAL OCTAVO VOL- 
UMES, of over 800 pages each, illustrated with about 4000 engravings, 
numerous FULL- PAGE PLATES, and FORTY MAPS; the whole, 
it is believed, forming the most complete work of reference extant. 
It is continually revised, keeping its information zcp to the ti/nes, 
especially regarding American matters. 

The design of this work, as explained in the notice prefixed to the 
first volume, is that of a DICTIONARY OF UNIVERSAL KNOWL- 
EDGE FOR THE PEOPLE— not a mere collection of elaborate 
treatises in alphabetical order, but a work to be readily consulted as 
a DICTIONARY on every subject on which people generally require 
some distinct information. The editors confidently point to the ten 
volumes of which it is composed as forming the most COMPRE- 
HENSIVE— as it certainly is the CHEAPEST— ENCYCLOPAEDIA 
ever issued in the English language. 

Great care has been exercised in the selection of writers who are 
recognized as authorities on the subjects treated of, and the result has 
been, as testified to by Mr. William Cullen Bryant, that " the 
different articles have the appearance of being furnished by writers 
having the most accurate knowledge of the subjects of which they 
treat. They are as free from abstruseness as may be consistently with 
scientific exactness, and, without being meagre, they are admirably 
concise. . . . It is just such a book of reference as every man 
has occasion for." 

The eminent historian, Hon. George Bancroft, LL.D., speaks of 
the Encyclopaedia in the following terms : " The work happily avoids 
superficiality without becoming cumbersomely scientific. The neat- 
ness of its typography is much to be commended ; the woodcuts are 
very instructive, and the maps are an important addition. I shall 
certainly keep it at hand as a most convenient and valuable book of 
reference." 



PUBLICATIONS OF J. B. LIPPIXCOTT dr CO. 

J, I llfPliCOTT & CO.'S IICTIOSIllS ' 

OF THE 

FRENCH, GERMAN, AND SPANISH LANGUAGES. 



CONTANSEAU'S PRACTICAL DICTIONARY. 

A Practical Dictionary of the French and English Languages. 

Composed from tlie French dictionaries of the Academy, Boiste, Be- 
scherelle, etc., from the Enghsh dictionaries of Johnson, Webster, 
Richardson, etc., .ind from technological and scientific dictionaries 
of both languages; followed by abridged vocabularies of geograph- 
ical and mythological names. By Leon Contanseau. Crown 
8vo. Extra cloth. $2 50. 
Prof. Contanseau was induced to prepare this work in consequence of 
the great inadequacy of all previous French-English Dictionaries to meet 
the wants of the student, which inadequacy was frequently brought to 
his notice during his professional career. 

CONTANSEAU'S POCKET DICTIONARY. 

A Pocket Dictionary of the French and English Languages. Being 

a careful abridgment of the Practical French and English Dictionary, 

preserving all the most useful features of the original work ; followed 

by abridged vocabularies of geographical and mythological names. 

By LfeoN Contanseau. i8mo. Extra cloth. ^1.50. Tourists' 

Edition. 2 vols. 32mo. Cloth flexible. In case. |5i.75. 

All the leading characteristics of the larger work have been retained in 

this abridgment, which was preijared for the purpose of affording those 

pupils, readers, and travellers, who object to the size or expense of the 

former, the benefit of a thoroughly good French and English dictionary 

of more portable size and at a lower price. 

LONGMAN'S POCKET DICTIONARY. 

A Pocket Dictionary of the German and English Languages. By 

F. W. Longman, Balliol College, Oxford. (Founded on Blakely 
and Friedlander's Practical Dictionary of the German and English 
Languages.) i8nio. Extra cloth. ^1.50. TOURISTS" EDITION. 
2 vols. 32mo. Cloth flexible. In case. ^1.75. 
"WcTiave not seen any pocket dictionaries (German or English) that can bear 

comparison with this. It is remarkably compendious, and the arrangement is 

c[ca.r. "—Lofic/on AthettcritDi. 

NEUMAN & BARETTI'S POCKET DICTIONARY. 

A Pocket Dictionary of the Spanish and English Languages. Com- 
piled from the last improved edition. iSmo. Extra cloth. $1.50. 
Uniform in general style and appearance with the Pocket Dictionaries 
of Contanseau and Longnuin, containing every word likely to be mel 
with by the traveller or the student. 



PVaLICATIOXS OF J. B. L/Pr/NCOTT &- CO, 



A MAGNIFICENT WORK. 



A CRITICAL DICTIONARY OF ENGLISH LITERATURE 

AND 

BRITISH AND AMERICAN AUTHORS, 

LIVING AND DECEASED. 

From the Earliest AccouBts to the Latter Half of the Nineteenth Century. Con- 
taining over Forty-six Thousand Articles (Authors), with 
Porty Indexea of Subjects. 

BY S. AUSTIN ALLIBONB. 

CofHf^ete in Three Volumes, Imperial Svo. 3140 pages. Fric^ per vol. i Extra 
Cloth, ^^7.50; Library Sheep, ^S.50; Half Turkey, i>q.y>. 



OPINIONS ON THE MERITS OP THE WORK. 
" As the work of a single man it is one of the wonders of literary industry. Every 

MAN WHO EVER OWNED AN ENGLISH BOOK, OR EVER MEANS TO OWN ONE, WILL FIND 

SOMETHING HERE TO HIS PURPOSE." — Atlatitic Monthly. 

" Far superior to any other work of the kind in our language." — Lord Macaulay. 

" All things considered, the most remarkable literary work ever executed by one 
man." — American Literary Gazette. 

"It maybe safely said tliat it is the most valuable and comprehensive manual of 
English literature yet compiled." — New \'ork Evening Post. 

"There seems to be no doubt that the book will be welcomed to innumerable read 
ing beings." — Thomas Carlyle. 

"As a bibliographical work it is simply priceless." — Neru Vo*-h Independent. 

" We are proud that it is the work of an American. We earnestly recommend ever) 
reader, student and teacher, and, we had almost said, every patriotic citizen, to secure 
a copy of AUibone's Dictionary of Authors." — Boston Evening Transcript. 

"A monument of unsparing industry, indefatigable research, sound and mpartial 
judgment and critical acumen." — IVashington Irving. 

" These volumes are treasuries of English literature, without which no collection of 
books in our moth.:r-tongue can be considered in any way satisfactory. They contain 
what can be possessed in no other way than by the ownership of whole libraries of 
books." — Philadelphia Ledger. 

" If the rest or' the work is as ably executed as that embraced under the first three 
letters of the alphabet, it cannot fail to be an important contribution to English litera 
I'dit."—IK H. Prescott. 

" No dictionary of the authors of any language has ever before been undertaken on sc 
?rand a scale. _ For convenience and trustworthiness this work is probably not sur- 
passed by any similar production in the whole range of modern literature. The authri 
has erected a monument of literary industry of which the country has reason to bf 
proud." — New York Tribune. 

•'■ In the English names alone Mr. AUibone's Dictionary will be far more complete 
ilian anv work of the kind published in the country." — London Daily News. 

Dr. William Smith, who is accorded to be one of the greatest compilers of the 
present age, has paid to the work of Mr. Allibone this generous tribute : " 1 have fre- 
quently consulted it, and have always found what I wanted. The informatioM is given 
in that clear style and condensed form which is so important in a dictionary." 

" Very important and very valuable."— CArtr/« Dickens. 



Special Circulars, contain it/g a full deseriptiofi 0/ the work, with specimen fag4t 
wUi bt UfU, Post-Mid, on apf>licution 



PUBUCATIONH OF J. B. UPl'INCOTT 6f CO. 

GET THE STANDARD. 

" Jt ought to he in ever;/ Library, nl.so in every Academy and 
every School."— Uos. Ciiaules Sumner. 

WORCESTER'S 

QUARTO DICTIONARY. 

A large, handsome volume of 1854= pages, containing 
<Jonsiderably more than 100,000 Words in its 
Vocabulary, with the correct Pronuncia- 
tion, Definition, and Etymology. 

Fully Illustrated. Library Sheep. $10.00. 
" W O K € E S T E It " 

(s now regarded as tlie standard authority, and is so recomuiendL'd by 
Bryant, Lonqfei.low, VViuttiki', Sunniou, IIoi-mes, Irving, Winthuop, Agassiz, 
Mak«h, IIknry, Evkrktt, Mann, QuiNcy, Feltox, IIili.aro, and tlio niiijority 
of our most distinguished scholars, and is, besides, lecogiiiEed as authority by 
dJbe P-^partmeuts of our National Government. 

THE COMPLETE SERIES OP 

WORCESTER'S DICTIONARIES. 

Quarto Dictionary. Illustrated. Library Slieep. $lu.OO. 
Octavo (Universal and Critical) Dictionary. 8vo. Library Sheep. 84.26. 
Academic Dictionary. Crown 8vo. Half roan. S'^.UO. 
Comprehensive Dictionary. Illustrated. r2mo. Ilalf roau. Sl.75. 
School (Elementary) Dictionary, T2mo. Half roan. $l.oo. 
Primary Dictionary. Hlusttated. IGmo. Half roan. 60 cents. 
Pocket Dictionary. Illustraled. 24mo. Cloth, 6>5 cents; Koan, flexfMt, 
85 cents; Jtoan, tucks, gilt edges, $1.00. 

Many special aids to students, in addition to a very full pronouncing 8*4 
dafining vocabulary, make the above-named books, in th« opinion of our most 
dlstii.ir»^i6lied educators, tlie most complete as well as by far the cheapest Diction- 
tuies of our language. 



"It follows from this with unerring accuracy that Worcester's Dictionary, beinj 
preferred over all others by scholars and men of letters, should be used by the youth 
of the country and adopted in tlie common schools." — New York Eccniny Post. 

"J. B. Lippincott <fc Co. are must fortunate in having secured the plates, even 
though at grejit expense, of Worcester's Dictionaries. The best English writers 
•,'id the most parlirular American writers use Worcester as tiieir authority It its 
«!mo6t incredible the labor represented in Worcester's unabridged." — AVu> York 
lUrald 



